Even prior to meeting Tsunayoshi Sawada and Reborn, Haru had already known a bit about Reborn, having watched him walk along her fence several times, where she gained an admiration towards him. Haru strongly disliked Tsuna, under the impression that he had corrupted the mind of Reborn, who previously stated that he was a hitman, her hatred towards Tsuna extended to Haru physically harming him.
Haru eventually befriends Bianchi, where she learns that Reborn truly is a hitman and Tsuna is the tenth boss of the Vongola. The next morning, Haru decides to test how strong Tsuna is with the use of samurai armor and hockey sticks. Due to the interference of Hayato, Haru fails to defeat Tsuna and is sent into river, and she's unable to swim due to the heaviness. She's rescued by Tsuna in Dying Will Mode, where her opinion on him changes and gains romantic feelings for him, much to his embarrassment. Haru mostly takes part in all of the crazy things that happen around Tsuna, or is a direct catalyst in them herself, such as when she attempted to help solve Problem 7, or when she thought Tsuna was abusing Lambo. In the manga, she, along with Kyoko, was shot with the Dying Will Bullet by Reborn when she ate one of I-Pin's Gyoza.
Haru makes only two appearances in this Arc, one of which she is not shown speaking. The first appearance she makes is when Tsuna is facing Birds, and Haru is shown on a projector screen wearing headphones and reading a book, unbeknownst to her that right behind her is one of the Bloody Twins awaiting Birds's order to kill her (the other Bloody Twin is behind Kyoko, in a different location). The second appearance she makes, she is shown in one of Tsuna's visions, after being shot by Leon's Rebuke Bullet, alongside I-Pin and Lambo, crying and claiming that Tsuna shouldn't have rushed Kokuyo Land, and insisting that she was going to be a Mafia Boss's wife someday, and she wouldn't cry over something like that.
Haru's main role is looking after Lambo during this Arc. She and Kyoko do so alternatingly with Nana Sawada. Sometimes Futa or I-Pin would help. Bianchi also helped and she knew about the Matches going on at night. She was saved from confrontation with the Varia the night of the Sky Match by Bianchi.
Arrival & Search for the Strongest Edit
Haru is thrust into the Future alongside Yamamoto, Kyoko, Lambo, and I-Pin during Adult Yamamoto's battle with Nosaru. She is knocked out by an attack from Nosaru but is saved by Yamamoto. She is escorted back to the Base by Hayato and Tsuna where she mainly helped to cook and clean along with Kyoko.
Haru, along with Kyoko, I-Pin, Bianchi, Chrome Dokuro, Futa, Reborn, and Giannini want the boys to tell them about the Millefiore and Byakuran. When they refuse, the two (her and Kyoko) go on strike against them living together. But after Bianchi explains their mindset to them, the two decide to call the strike off.
Haru, whilst working in the kitchen, is approached by Tsuna, who sits her down and explains everything about what's going on with the mafia. She pretends that nothing is wrong, but after he leaves and Bianchi walks in, she breaks down and cries. Haru said that even though she knew the truth, she didn't know how serious the situation was, and therefore she felt that she was very selfish when she didn't know anything.
Haru is seen returning to the past alongside the rest of Tsuna's Family.
After returning from the past with the rest of Tsuna's Family Haru is seen cooking and cleaning with Kyoko and Uni. However they are interrupted when Zakuro, one of the real Six Funeral Wreaths, attacks the Vongola Base. Haru and the other non-combat personnel are escorted outside by Tsuna and his Guardians. Tsuna, who is at a loss for where to hide Uni for the time being, decides to follow Haru to the Kawahira Realtors shop. Haru states that she knows the old woman who ran the shop and apparently even offered Haru sanctuary in case she ever decided to run away from home. She also seems to have knowledge of the shop's interior where the old woman, or Obaa-chan as Haru calls her, fed her snacks. She uses this knowledge to effectively hide everyone within the shop. It is unknown if Haru has any connection to the shop's current owner Mr. Kawahira in the past or the future.
Haru doesn't have much of a role in this arc compared to the previous ones. She only made a small cameo with Kyoko when Tsuna and the others were preparing to face off against the Simon Family. She and Kyoko were at a cake shop and when Tsuna ran off, she asked Kyoko what was wrong; not knowing that Tsuna had left, silently saying goodbye to them.
Haru makes a brief appearance in the last arc, where she is shown standing outside Tsuna's house with Tsuna's Guardians and Kyoko. Prior to this, Tsuna had saved her from getting injured by some falling construction equipment, causing her to blush and call him her hero.