She was once a girl named Nagi, she lived an isolated and antisocial life. After trying to rescue a cat, she was severely injured in a car accident, which led to the loss of her red eye and some internal organs.
Nagi was taken to the hospital, where the doctors informed her mother that the only way her life could be saved is if someone with the same blood type transferred their organs to her. Nagi's mother didn't care whether or not she lived and refused to sacrafice her own lives for her organs. Unbeknownst to her mother, Nagi was conscious and heard the conversation, in the process she lost her will to live and accepted her death. Before killed, she was saved by Mukuro Rokudo, who heard her words and lived by creating illusionary organs. When Nagi is revived, she realizes her meeting with Mukuro was real and cries in relief and happiness, Mukuro provides her with a new name. Chrome Dokuro.
She immediately ran away from the hospital and went to the neighbor town, Kokuyo as ordered by Mukuro. On her way there, she stopped Ken Joshima asleep on the nearby park. Under the belief that he looks like he's going to die, she sits his head on her lap to make it comfortable for him to sleep. When he awoke, he was surprised, causing him to shout angrily at Chrome until he feels hungry. Realizing this, she gave him an apple, which reminded Ken of his past when Mukuro also gave him an apple when he and Chikusa Kakimoto were hungry, he tearfully eats the apple and leaves the park.
Unknowingly to him, Chrome follows them all the way to Kokuyo Land. Ken and Chikusa were already aware of her due to her connection with Mukuro that they were informed about prior. She explains to the two that Mukuro ordered her to accompany them until he's freed from Vindice Prison. In response, Ken decides to cut Chrome's hair into a shorter style, matching that of Mukuro, and the two let her stay in Kokuyo Land with them.
Chrome was chosen to be the hoder of the Half-Vongola Mist Ring, she introduces herself in the school gymnassium of Namimori Junior High. At first she's assumed that it's actually Mukuro in disguise by Hayato, who points out that her eyepatch suspiciously covers his right eye. In spite of Hayato's remarks, Tsuna believes that she's not Mukuro, and Chrome responds by giving Tsuna a kiss on the cheek as a form of greeting.
She faces off against Mammon during the early stages of her match, but was overwhelmed once Mammon got a bit serious. Mammon, soon realizing that her trident was the key to her power, began targeting that, and, shortly after, was able to destroy it.
This led to an unusual phenomenon where Chrome lost some of her organs, and seemingly lost the match. She collapsed and her stomach caved in. On the verge of defeat, Chrome briefly remembered her past and cried as she communicated with Mukuro, telling him that she wanted to help him. Responding to her call, Mukuro told her to rest and her body covered with mist, switching place with Mukuro and quickly turned the tide. Mukuro soon defeated Mammon, winning the match, but having used too much of his power, his grip on his real illusion faded, returning the body back to Chrome. She was then taken to Namimori Hospital since Ken and Chikusa refused to take her back with them. The next morning, she met Tsuna when he intended to visit Lambo and she assured him that Mukuro will be alright before returning to Kokuyo Land.
In the Cloud Ring Battle, she, Ken, and Chikusa watched Hibari's fight against Gola Moska. When the Gola Moska went on a rampage, she ran as she tried to evade the attack, but accidentally stepped on mines buried within the battlefield. She was saved by Ken and Chikusa, but the three were then cornered between the rampaging Moska and gattling gun until Tsuna saved them.
In the Sky Ring Battle, she was captured by Belphegor and Mammon and held hostage to convince Gokudera and Yamamoto to give up their Rings. Gokudera and Yamamoto attempted to save her but were caught in an illusion; however, Ryohei came to the rescue and broke the illusion. When Mammon attempted to escape after all fifty Varia backup members were defeated by Lancia, she prevented him from escaping.
According to Kusakabe, five years before Tsuna and the others were transported to the Future, Future Chrome, Ken, and Chikusa attempted to break Mukuro out from Vindice Prison but the attempt failed and the three were separated, their status, unknown. However, five years afterwards, half a year before Tsuna's arrival to the future, Glo Xinia was said to have defeated Mukuro while he was possessing Chrome. Before he could defeat her too, Future Chrome escape by throwing herself out of the window. She later encountered Guedo Greco at airport in Italy while he was being possessed by Mukuro, and instructed her to go to Kokuyo Land.
Reaching Kokuyo Land, Future Chrome was replaced by her past-self who was then confronted by Glo Xinia and is quickly overpowered. But with the help of Future Mukuro, she was able to thaw out her Ring and defeat him. Ryohei later brought Chrome to the Vongola Base. As she lay in bed sick, her illusionary internal organs begin to fail and disappear due to Mukuro's defeat by Byakuran. However, she was able to use the Vongola Mist Ring to sustain her organs via her own Illusions with thanks to Hibari's instruction. During the Invasion of the Merone Base, she appeared using Illusions to disguise herself with Hibari, Kusakabe, Lambo, and I-Pin. Along with the other Vongola Guardians, Chrome was given a Vongola Box Weapon.
Back to the past to participate in the Arcobaleno Trials, Chrome was visited by Mukuro in the illusionary world. Mukuro asked where she was for the past three days, but Chrome was unable to answer and Mukuro let her to keep it to herself. Mammon, disquised as Tsuna, confronted Chrome and demanded her to call Mukuro, frightening her and prompting Mukuro to switch place with her until Tsuna cleared Skull's trial. Tsuna later gave her a bento, remembering that Chrome didn't eat much back at the future, which Chrome gratefully accepted.
During Reborn's trial, Chrome and the other Guardians fights Reborn, but they were easily defeated. She later also participated in Verde's trial, helping Tsuna and the other Guardians to fight the prototype Box Weapons that Verde created. After Tsuna received both seals from Reborn and Verde, she returns to Kokuyo Land and once again communicates with Mukuro who asks her involvement with Vongola and Arcobaleno, but didn't force her when she was reluctant to answer since all that matters is she is safe. The next day, she returned to the future with everyone, preparing for the Choice Battle.
Upon returning to the Future, the other members of the Famiglia were at first worried that Chrome wasn't eating. However, once she established a friendship with I-Pin, she began joining them for dinner. She later began training to master her Illusions with the virtual training challenge created by Mammon and her combat abilities with Bianchi and I-Pin. Chrome was not one of the participants in Choice and therefore watched the battle from the Vongola viewing area.
After being sent back to the past for the Inheritance Succession Viper was chosen to be Chrome's tutor. Chrome later went missing for several days only to return to Kokuyo Land, greatly upset and crying. Upon being questioned by Kyoko, Haru and I-Pin, she stated that she no longer wished to fight, leading the other Guardians to think she would be better off staying in the past with the other girls. It was later revealed that Vongola first Mist Guardian Demon Spade had taken control of Chrome in order to draw the girls out and hold them as hostages. The group was then trapped in an illusion with limited oxygen, and while the other Guardians attempted a rescue, Chrome attempted to break the illusion. With Viper acting as a guide, she was able to accomplish. Later Demon gave Chrome her inheritance after expressing an interest in Mukuro, who had appeared briefly to save Chrome.
After returning from the past, the Six Funeral Wreaths tried to capture Uni. Chrome used her Vongola Mist Owl Cambio Forma to see through the enhanced illusions created by Torikabuto, aiding Tsuna in his fight. During the day of the final battle, Chrome delivered the Vongola Mist Box to Mukuro but fainted shortly after seeing him for the first time. After Byakuran was defeated, M.M warned Chrome that Mukuro was only using her to escape from prison. Before Chrome could respond to this, they were interrupted by Ken, Mukuro, and Chikusa who told her that it's about time to return to the past. As she faced Mukuro, she said that she's also happy to finally able to meet him in person. Once she returned to the past along with the others, she smiled as she looked at her Mist Vongola Box Ring before switched placed with Mukuro.
Back in the past Chrome was stalked by Julie Kato, a transfer from Simon Middle School, who also secretly started delivering foods to her. He later introduced herself and asked her to go on a date and run away with him after the inheritance ceremony. However, she softly rejected him and just left him standing there, making Julie commented that she's cute.
Later, after Yamamoto was attacked, Chrome created an illusion of him for Tsuna's Inheritance Ceremony so that the other Mafia members would remain unaware of his absence. During the inheritance ceremony, she, along with the other guardians (excluding Lambo), was defeated by Enma. When the Simon Famiglia took their leave after Enma defeated Tsuna, she was taken along by Julie, dropping her Vongola Ring and Animal Ring on the ground in the process.
After awakening to find herself trapped at Simon Island, Chrome attempted to escape but was stopped by Julie who demonstrated that he was creating her illusionary organs for her as the Island had a barrier that prevents Mukuro's illusions from passing through. When Chrome refused his offer to become his, Julie then explained that he was responsible for the entire battle between the Simon and Vongola for two goals, first for complete annihilation of Vongola and second was her. As he said this, he revealed his true identity as Demon Spade in disguise. When he requested for Chrome to submit her body by her own will, she refused and Demon then punished her by proceeding to take control of Chrome's mind in order to draw out Mukuro so he can take his body.
She's seen again alongside Daemon, after he finally revealed his true identity and plans to Tsuna and the others. She creates a mist barrier that traps Tsuna and the others with her technique, Cortina Nebbia, to prevent them fighting Demon all together at once. Hearing Demon Spade's intention to take over Mukuro's body, Hibari threatened Demon by breaking the barrier, but Demon warned Tsuna and the group that if the barrier is broken; Chrome, the creator, will be killed. When Yamamoto managed to injure Demon with his new technique, Chrome interfered and refused to step back until Demon ordered her to. Before she left the battlefield with Daemon, Yamamoto gave her the Ore of Mist Version X and told her that they will always wait for her.
The next day, when the Simon Ring finally fully awakened, she was tied up as Demon undid the mind control on her and told her that he will let her meet Mukuro. Chrome asked why now, which he replied that it's a perfect time because he can fight Mukuro with the fully awakened Desert Simon Ring. Chrome realized that he was using her as a bait to lure out Mukuro and shouted that she won't let it happen. Demon replied that no one is there to listen to her opinion, since the one who will decide is Mukuro and he opened the barrier of the island. Chrome urgently pleaded at him to stop, but it's already too late and Demon removed her illusionary organs to lure out Mukuro; as Chrome spit out blood, she silently pleaded Mukuro to not come but soon blacked out. After this, mist surrounded Chrome and Mukuro appeared, replacing her.
After the fight of Mukuro and Daemon, Mukuro leaves Chrome to Tsuna and changed back into Chrome. When she woke up she asks where is Mukuro and Tsuna replied that Mukuro had already defeated Daemon, making her glad. However, Chrome and the others were shortly surprised when they heard Mukurou, the box animal, speaking and knew that there was trouble regarding Mukuro's body in Vindice. Julie suddenly woke up and asked about the situation. Tsuna and Gokudera said that Demon is still alive and is inside Julie which Chrome and Mukuro immediately replied that he is no longer Daemon. Mukuro concluded that Demon had taken over his body, surprising them. At the confrontation with Daemon, she was saved by Yamamoto from being sent to Demon Spade's illusionary world. She intended to assist Tsuna and Enma to see through Demon Spade's illusions but Demon threatened that he will kill her with Mukuro and Reborn if they were to assist them and told them to watch. However, she finally interferes when Tsuna hesitates to shoot Enma along with Demon by protecting Enma with her Barrier Mist Flames in full power that were also supported by Mukuro. After Demon was defeated, she and the others returned to Namimori, with Mukuro freed by the Vindice after acknowledging his effort during the battle with Daemon.
Transfer to Nami-Middle Edit
Tsuna and the others are surprised to see that Chrome has been transferred to Nami Middle. She stood at the front of the classroom to introduce herself, but breaks down crying in Kyoko's arms. When discussing this between classes, Ryohei told them that according to what Kyoko has heard from Chrome, she was kicked out of Kokuyo Gang by Mukuro. When she woke up in the morning, she only found a note that telling her to get out and a Nami-Middle uniform, and Kokuyo Land already empty. Gokudera then commented that since Mukuro was free from jail, he doesn't need Chrome anymore. Tsuna seemed to have doubts about that representation of events. Reborn then arrived and told them that he was convened by Mukuro to talk about Chrome and was given her living expenses by Mukuro as well. Since Chrome has already arrived in Namimori, Reborn said that settling her in to either Kyoko or Haru's house would be for the best until they found a place for her to live. Reborn then suggests a welcoming party for Chrome at Tsuna's house, with the theme of a mimicry contest. At the party, Chrome thanks everyone for throwing it for her with the moral support of Haru and Kyoko and holding a mimicry contest where the loser must become Chrome's errand boy for a year.
1st Day of Representative Battle of the Rainbow Edit
Later on the first day of the Representative Battle of the Rainbow, during classes, she was shown to be having a cold. After school, on her way home, she was approached by illusion that Mukuro created to check on whether she was getting better or not. However, seeing her, he states that her condition has worsened as he had thought. Mukuro tells Chrome to tell him everything about her condition; otherwise, she was going to die, much to Chrome's shock. The next day, Tsuna noticed that Chrome was not present at school and wondered did something happened to her.
3rd Day of Representative Battle of the Rainbow Edit
After the second Representative Battle of the Rainbow, when Tsuna, Gokudera, and Yamamoto visited the hospital to check on Team Skull's condition after defeated by Team Bermuda, they bumped into Kyoko, who told them that Chrome's internal organs are gone. Tsuna rushed into the ICU and saw that she was really worn out. Tsuna apologized for not acting upon her absence even though he noticed it, but Chrome ignored his apology and instead requested Tsuna so she could be placed on Team Reborn. Tsuna refused as Reborn is the one who decides on the team and worried about her condition, but Chrome still pleads to him; despite that, Tsuna still refuses. Later, however, during the battle between Team Reborn and Team Verde against Team Bermuda, Chrome appeared at the battlefield as Reborn's sixth representative and offered to support Mukuro's illusion, joining the fight. At this moment, the cause behind Chrome's illness is revealed; With Mukuro freed from the Vindice prison, Chrome began to contemplate her own existence as a separate person from Mukuro, bringing her into an internal conflict with herself, which in turn made her slowly reject Mukuro's illusions that projected her organs, which slowly deteriorated her health. However, remembering Reborn's question of what she wants to be to Mukuro, she finally found her resolve to protect people that she loves. Chrome was able to recreate illusionary organs with her own power and by using Verde's equipment, assisted Mukuro's illusion. By combining both of their illusions, they able to create a much more powerful version of Genjū Gagaia, Genjū Mugaia
4th Day of Representative Battle of the Rainbow Edit
Chrome didn't return to Kokuyo Land for unknown reason and met Tsuna and Kyoko during her way to school. After school, she, along with Kyoko, Haru, and I-Pin went to Tsuna's house after fixing the lucky charms for Tsuna, Gokudera, and Yamamoto. They were surprised when seeing large amount of people gathering at Tsuna's house. Bianchi told Kyoko and Haru to leave the house until the meeting is over while Chrome stay to join the meeting and was chosen as one of the representatives who will fight in battle against Team Bermuda.
In the afternoon, after the watch announced the start of the battle, she, along with Gokudera, Yamamoto, and Fran fought against Small Gia and Big Pino. She creates illusions with Fran to buy some times until Tsuna, Enma, and Basil arrives after defeating Alejandro. However, Small Gia and Big Pino able to located them and destroyed their illusions, exposing them. Fortunately, before Big Pino's next attack could hit them, Enma used his gravity manipulation to float four of them into the air, saving them. When Tsuna's vision was blinded by one of Small Gia's weapons, Yamamoto and Gokudera immediately interferes and with Enma's help, straining the two Vindice's movements.
As they're straining them, Gokudera asked for Chrome's help for their plan. Chrome immediately told Fran to protect them with Verde's device. Fran at first, refused, since he's tired, scared, and annoyed, but, after her firm insistence, he agreed under condition that she'll kiss him on cheek if it goes well. With her aid, Fran created ceramic that covered Gokudera's and Yamamoto's body as the dynamites explode, destroying Small Gia's and Big Pino's wrist watches without harming the two. After recovering from the previous battle, she and the others went to where the remaining team members are. She, Enma, and Fran helped Tsuna from Jaeger's attack, but quickly defeated in instant, rendering them unconscious. Later, her watch, including the other fallen members' watches, are destroyed by Bermuda to prevent them from assisting Tsuna.
After Bermuda was defeated, she, Mukuro, and Fran are submitted into Namimori Hospital along with the Varia, Byakuran, Dino, Basil, and Hibari. She was seen in Mukuro's room along with the other members of Kokuyo Gang who were visiting him when Hibari destroyed the wall that lead to Mukuro's room. In the last chapter, several days after the battle, Chrome is last seen in front of Tsuna's house, waiting for him along with the others, invited by Reborn to celebrate Tsuna's tutelage.