Before going to school, Yamamoto is practicing with his bat. He starts a conversation with the owner of the club, saying that he still has a long way to go. At that time, Reborn arrives and tells him to train more and falls asleep immediately afterwards. Yamamoto brings Reborn back to his family's sushi bar. Tsuna then arrives and begins to tell off Reborn and apologizes to Yamamoto. However, Yamamoto brushes off his apologies and Reborn reveals that he's there to strengthen Yamamoto, he also points out that the school is closed for the day due to the school's opening anniversary.
The three leave the bar and arrive at the school with Yamamoto excited to train with Reborn. Reborn gives Yamamoto a small ball and tells him to aim for the mark on the pole. When Yamamoto throws the ball, spikes suddenly release from inside and destroy the ball, much to Tsuna's surprise. However, Yamamoto concludes that the pole is made of foam and that Reborn is trying to boost his confidence. However, Tsuna checks and sees that the 'foam' is real concrete.
Just then, Gokudera arrives and asks Tsuna if he is really going to fire Yamamoto. However, when Tsuna explains that Yamamoto is training and is receiving some weapons, a disappointed Gokudera tells him that Yamamoto should throw grass instead. Reborn gives Yamamoto a heavy baseball bat which can be used as a telescope. Yamamoto looks through it and dodges a bullet which came from Dino and his men. Reborn then announces the continuation of the training. Yamamoto manages to get Tsuna to play with him too and Reborn tells Gokudera to attack them too. Yamamoto easily dodges the bullets and the explosions causing Reborn to shoot him too. Yamamoto defends with his bat which turns into a sword. Yamamoto is overjoyed by Reborn's gift and is able to hit all the targets when he goes practice baseball the next day...
Note: Bold + Italicized = First Appearance