Returning home from school, Tsuna is surprised to see a group of men in black suits surrounding his house. The guards try to stop Tsuna from entering but lets him enter when he introduces himself. Inside, Nana comments that she didn't know her son had such a handsome friend. Tsuna hurriedly goes to his room to confront Reborn and is surprised to see another Mafia boss waiting for him. The boss introduces himself as Dino the tenth boss of the Cavallone Famiglia. After one look at Tsuna, he starts to pick on Tsuna, commenting that Tsuna doesn't have what it takes to be a boss. However, he apologizes upon seeing Tsuna's dismay. Reborn introduces Dino as Tsuna's senior apprentice and his former student. As Dino and Tsuna start to get acquainted with each other, I-Pin and Lambo arrive. Lambo accidentally trips and lets go of his grenades that start to fall to Dino's subordinates outside the house. However, Dino is able to save his subordinates causing Tsuna to admire him. Reborn invites Dino to stay for the night while his subordinates leave.
Later that night, Dino asks Tsuna about his family but Reborn is the one who answers and tells him about Gokudera, Yamamoto, Hibari and Ryohei. As the conversation continues, Dino accidentally spills his food and Reborn explains to Tsuna that without his men, Dino is a serious klutz. As Nana Sawada leaves to prepare their bath, she screams after seeing Dino's pet, Enzio, eating the tub. I-Pin tries to stop Enzio but fails since her attacks are ineffective. Dino tries to use his whip but ends up injuring Tsuna, Lambo and I-Pin instead. However, Reborn uses Leon to make a mask of Romario which allows Dino to restrain his pet and return it to normal with the help of some blow driers. However, without his men, Dino is nothing more than a klutz...
Note: Bold + Italicized = First Appearance