Ni-Hao Gyoza Fist! is the 6th episode of the Katekyo Hitman Reborn! anime.
In the morning, Tsuna again wakes up late for school. He bumps into Bianchi in the bathroom, hands her a towel, and promptly runs out. She laughs, commenting on his immaturity. While he tries to go to the other bathroom, Lambo is instead inside and refuses to come out. Tsuna wonders why there were so many strangers inside his house. At breakfast, when Tsuna has dressed, Reborn eats his food right after it was given to him, and comments that Tsuna would have to be quicker in order to succeed. As there was no time left, Tsuna rushes out the door to go to school.
Outside, while Tsuna is walking, he sees a street vendor selling gyoza buns, and another child running away after looking at a paper. He orders one, and, while walking, mocks the chihuahua from before with it. A larger dog comes and opens the gate. While panicking, Tsuna notices that the kid from before has appeared and warns him about the dog. However, he appears capable of psychic powers and seemingly makes the dog float inside the gate. Tsuna thanked him, but he merely wrinkled up his face and ran away.
At school , Tsuna tells Gokudera and Yamamoto about the kid. They, along with Reborn, scoff at him, saying that there was no such thing. After this we see the kid walking around town, showing random people the photograph he was looking at earlier; however, no one seems to recognize the picture. At school, while cleaning, Tsuna sees the kid talk with Kyoko and Hana. He finds out that they know him because he had lent them money, and comments that he was really nice. The kid takes out the photograph again, and, upon looking at Tsuna, issues a challenge to him.
Later on the roof, Tsuna sees the kid again, in a martial-arts position and eating gyoza. He says that he had misjudged Tsuna before and was now going to defeat him. Reborn, up on a platform, comments that he was the "so-called kid with a deadly arm," I-Pin, whose other nickname was the "Human Bomb." Tsuna is dealt the same attack used on the dog earlier, and is unable to find the secret that Reborn mentioned, after which Reborn shoots a bullet into the area. A puff of ginger-colored smoke rises out, and Tsuna smells garlic. Reborn says that the technique is called Gyoza-Kempo, and that the garlic directly affects with the brain, so it seems that the target is moving out of its own accord. Tsuna calls this technique "silly," after which I-Pin starts sweating rapidly and mahjong symbols appear on his head. Reborn informs Tsuna that he has just started the Pinzu-Timed Super Explosion, that it was a result of I-Pin's shyness and was strong enough to create a crater, and the reason why I-Pin was called the "Human Bomb."
Kyoko shows up, and I-Pin attaches himself to her leg. Reborn says that during the countdown, I-Pin attaches himself to anything nearby. He pulls him from her leg and throws him, straight into the arms of Gokudera, who passes him back to Tsuna. Tsuna then throws it at Yamamoto, but again Yamamoto throws it in Tsuna's direction. Reborn fires the Dying Will Bullet, and Tsuna, in Dying Will Mode, saves everyone. They find out that Tsuna was not the person in the photograph, and that I-Pin is extremely nearsighted.
At dinner, Tsuna finds out that I-Pin has decided to train in Japan. Lambo appears, and I-Pin, mistaking him for a broccoli monster, begins a rampage. Gokudera, Yamamoto, and Haru show up in the middle of it, and I-Pin calls Haru a dumpling monster. Lambo is insulted and begins calling I-Pin names, after which she begins her countdown. However, before she could explode, they shoot her with the Ten-Year Bazooka, and find out that I-Pin is actually a girl and that she gave up her martial arts, with her countdown being sealed with a password. However, after she sees Lambo, they find out that the password is actually "broccoli monster," and she explodes. When everyone wakes up, the five-year-old I-Pin is back.