As Tsuna walks through the streets, he teases a barking dog on the other side of a gate but ends up running when the gate opens. As Tsuna tries to run for his life, he sees a Chinese kid who beats up the dog without directly touching it, surprising Tsuna. Later, Tsuna returns home and starts to tell Reborn about the kid but is surprised to see Reborn surrounded by Dragonflies. When the bugs leave, Reborn informs Tsuna of an assassin from Hong Kong, also known as the Human Bomb, named I-Pin's arrival.
The next day, as Tsuna helps clean the school hallways, he spots Kyoko and Hana talking to the kid from yesterday. Before leaving, the kid approaches Tsuna and points upward, much to his confusion. Tsuna walks to the roof and is confronted by the kid, saying something in Chinese. Reborn translates what the kid said and tells Tsuna that the kid is the assassin, I-Pin, and that he is her target. As Tsuna almost gets choked to death, Reborn uses his gun to reveal the secret of I-Pin's technique. When Tsuna realizes that I-Pin is using some stinky kempo, he starts to laugh causing her to be shy and use her Pinzu-Timed Super Explosion. As the countdown starts, Kyoko and Gokudera arrive and the group begins to pass I-Pin around until Yamamoto arrives and throws I-Pin away, saving everyone from the explosion.
Tsuna, Reborn and Gokudera tie up I-pin and bring her home where they find out that I-Pin's target is not Tsuna and that she is also extremely nearsighted. I-Pin decides to stay in Japan in order to train since she still has a long way to go before becoming a professional.
Note: Bold + Italicized = First Appearance