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Fuuta de la Stella (lit. Fuuta of the Stars) is a young boy who ranks people by their abilities in his Ranking Book half his own height that somehow fits inside his jacket pocket. He has an extremely wide range of knowledge on thousands of people and is considered to be an invaluable informant for the mafia, sometimes being paid insane amounts of money for a copy of certain rankings.
When he starts ranking people, gravity around him becomes distorted, making objects around him float and images of stars and galaxies appear in his eyes. It is unknown how he actually gathers his information (some say he communicates with the Ranking Planet in the galaxy), but if he does not instantly write it down, he claims to forget about it. Rain weakens Fuuta, however, resulting in his rankings being somewhat incorrect and random when it rains. He also has to be looking at the person to determine their rankings. Still, when done right, his rankings are said to be 100% accurate and if a person gets hold of his book, they would have the world at their mercy.
He calls Tsuna his big brother and has ranked him last on every aspect of combat, but was overjoyed to see that his rankings on him were wrong, not realizing Tsuna was in Dying Will Mode. Fuuta's book is the reason why he is constantly being chased by the mafia, so Tsuna allows Fuuta to live in his house.
Fuuta is introduced as he is ranking Tsuna. As Tsuna awaits for Fuuta's ranking to be done, Fuuta comes to the conclusion that overall Tsuna is dead last. Throughout the Arc, Fuuta takes on the role of Tsuna's younger brother. He participates in the snowball fight that they have, only to disappear from having Enzo fall on him.
Prior to the events of the Arc, Fuuta is possessed by Mukuro, who attempts to coerce him into making a Ranking of Tsuna's Mafia Family. Due to Omerta, Fuuta doesn't comply, and Mukuro is forced to send Ken and Chikusa out on older information.
Once Tsuna's group makes it past Ken, M.M., and Birds, Fuuta announces his allegiance to Mukuro, prompting Tsuna to follow him into the woods as the rest of the group have a showdown with the Fake Mukuro.
Fuuta doesn't reappear until Tsuna, Bianchi, and Reborn make it to Mukuro's Hideout. He impales Bianchi in the stomach with the knife of Mukuro's Trident, knocking her unconscious. Then he attempts to stab Tsuna, who escapes by tangling him up, knocking the knife of the Trident away, and telling Fuuta that it isn't his fault that everyone has to fight. Fuuta passes out and sleeps for the first time in ten days.
Fuuta, in the beginning of the Future Arc, was away from the Base on business with Bianchi in order to gather intelligence on the Millefiore hideout. After Lal, Tsuna, Gokudera, and Yamamoto return from the search for Kyoko and the battle with Gamma, they return with that information.
Later, Fuuta is seen during the start of Tsuna's training battle with Hibari. He tells Lambo about how he was his Guardian until three years prior. Noting that he is not allowed to tell him any more than that, all he wants to get through to Lambo, is that "This is all very dangerous." During a filler episode, it is revealed that Fuuta has gained extensive technological know-how, evidenced by the fact that he is easily turned to by Giannini to go and repair faulty wiring disrupting one of the main cameras. Also, despite the fact that he has yet to rank something in the future, certain aspects of his ranking power are shown, such as his ability to detect rain when inside a windowless building.
Fuuta also appears to be much more mature.
Future Fuuta went with Tsuna and the rest of his family into the Choice arena and comes face to face with Byakuran and the Real Six Funeral Wreaths. He's not a participant and remains as a spectator in an enclosed area.
When Tsuna and the rest of the family is transported back to the past, they met with the worried younger Fuuta who believes that they disappeared because they got lost after a picnic trip. He later watches Tsuna, Lambo and I Pin leave the house to return to the future without even knowing where they are going, he gave them an encouraging phrase, "Good luck!".
In his future form, Fuuta watches Tsuna and Byakuran's fight. Later, after Tsuna has defeated Byakuran and the people from the past are about to return to their timeline, Fuuta sadly states that he wouldn't be able to play with I-Pin and Lambo anymore; however, Lambo cheerfully states that they would still play with him, and Fuuta brightens up, telling Lambo and I-Pin to play with his younger self in the past.
Fuuta first briefly appears handing Tsuna a glass of water after giving Lambo and Reborn a bath, complimenting Tsuna on his hard work. Later, when the CEDEF arrive and Nana scolds Tsuna for talking rudely to his dad Iemitsu, Fuuta expresses his shock that Nana actually got angry.
- According to Fuuta, there are 86,202 people in the Mafia that he has seen.
- Future Fuuta hasn't been shown to have made any rankings thus far
- The future Fuuta still calls Tsuna "Tsuna-nii."
- In the manga adaption in America, Mukuro states that Fuuta hadn't slept in ten years; however, the present Fuuta is only 9.
- Mukuro also stated that Fuuta, in order to keep the Vow of Silence, refused to speak, causing him to close his heart; and, as a consequence lost his ability to rank. This may be a reason for why Future Fuuta has thus made no rankings.
- Fuuta was featured in Yakusoku no Basho e - vs. Millefiore.
- In the Filipino version of Reborn!, Fuuta's name was changed to "Kuta" because Fuuta's name sounds obscene in the Philippines.
- Fuuta is most likely a reference to the famous autobiographic allegory, "Le Petit Prince" by Antoine de Saint Exupery, hinted by the fact that the chapter he appears in is named "Le Petit Prince Fuuta," as well as wearing a scarf similar to the Little Prince's. The book is about a boy who lives on a small planet and travels from planet to planet, learning an important life lesson at every stop.
- He has the same voice actor as Lavina, the mother of Hayato Gokudera.