Futa is introduced as he is ranking Tsuna. As Tsuna awaits for Futa's ranking to be done, Futa comes to the conclusion that overall Tsuna is dead last. Throughout the Arc, Futa takes on the role of Tsuna's younger brother. He participates in the snowball fight that they have, only to disappear from having Enzio fall on him.
Prior to the events of the Arc, Futa is possessed by Mukuro Rokudo, who attempts to coerce him into making a Ranking of Tsuna's Mafia Family. Due to Omerta, Futa doesn't comply, and Mukuro is forced to send Ken Joshima and Chikusa Kakimoto out on older information.
Once Tsuna's group makes it past Ken, M.M.., and Birds, Futa 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.
Futa 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 Futa that it isn't his fault that everyone has to fight. Futa passes out and sleeps for the first time in ten days.
Futa, 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 Mirch, Tsuna, Gokudera, and Yamamoto return from the search for Kyoko and the battle with Gamma, they return with that information.
Later, Futa 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 Futa 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.
Futa also appears to be much more mature.
Future Futa 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 Futa 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, Futa 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, Futa 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 Futa brightens up, telling Lambo and I-Pin to play with his younger self in the past.
Futa 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, Futa expresses his shock that Nana actually got angry.