Isla is a female Giftia with twin-tails and has a childish appearance which causes those around her to feel the fleetingness of life. She is a veteran at the department Tsukasa works in and was also partnered with Kazuki in the past. After that, all she does is serve tea for her fellow co-workers. When Tsukasa arrives, she becomes his partner and goes back into the field again. She is extremely clumsy and retreating in personal life, but her true personality is revealed to be slightly childish, lively, fun loving and caring.

Tsuna is set to become the tenth generation boss of the Vongola family. In school, Tsuna has been given the harsh nickname of "No Good Tsuna," as he is very clumsy, gets low marks in school and is somewhat of a pushover. Although he is the tenth generation Vongola boss, Tsuna is unwilling to take part in anything that has to do with the Mafia. He always denies the fact that he is a future Mafia boss and tries to avoid anyone involved with the Mafia. In the Future arc he states that he would rather destroy the Vongola family than accept its bloody history. Tsuna is often surprised and horrified (for a comedic effect) at Reborn's and other mafiosos' actions. Later, even though he still wants nothing to do with the Mafia, he is grateful for the friends he has made since meeting Reborn. He cares a lot for his new "family" and would put himself in the way of danger in order to protect them. There have been many parallels that link Tsuna with the first boss and founder of the Vongola family, Giotto. Both of their personalities are likely to be very similar as it has been shown that they have similar goals and ways of standards.