Natural Born Hitman

Yamamoto has a natural talent for most every physical activity he tries. From baseball to swordsmanship Yamamoto is able to pick it up quickly and with far less effort than his peers. Yamamoto's skills come so easily that he could arguably be called a prodigy. A prodigy is defined as being someone, usually under the age of 18 that has mastered one or more skills far beyond their level of maturity. While I feel it would be a stretch to consider Yamamoto a baseball prodigy, though he is certainly unrivaled on his school team, he could be called a prodigy of swordsmanship without a doubt.

Yamamoto first held a sword when Reborn tricked him by making him believe it was a training baseball bat. He used that for the first arc or two, using the transforming weapon as more of a sharp bat than a true sword. It wasn't until the Varia Arc when he lost to Superbia Squalo, The Sword Emperor. Squalo is a master assassin and swordsman who told Yamamoto he had no idea how to use a sword. This encouraged Yamamoto to take lessons from his father, a sushi chef and retired swordsman. Yamamoto is only given three weeks of training during which, per the rules of the Shigure Souen Style, he was only able to observe each of his father's techniques once before having to learn to master it.

All too soon Yamamoto is forced to face Squalo again in a life or death battle. During his second battle, Yamamoto shows considerable skill with a sword. Yamamoto is able to dodge Squalo's attacks and while his technique is still a little rough around the edges he is able to hold his own against a mature and accomplished swordsman. Yamamoto's victory is somewhat of a fluke caused by Squalo's overconfidence. Squalo had seen a different variation of the Shigure Souen Style which led him to believed he knew what Yamamoto intended to do. Even with that consession, the fact that an amateur swordsman with only a few weeks of experience stood his own against one of the most accomplished swordsmen in the world, a man who had fought a hundred battles to earn the title of Sword Emperor is impressive and it speaks to Yamamoto's natural talent. His skills are so great that even Reborn comments on Yamamoto's abilities as a "natural born assassin".

Yamamoto's skill continues to grow as they face further enemies, during the Future Arc, Yamamoto is trained by Reborn who selects Yamamoto among the guardians to share secrets because he knows Yamamoto will be able to make use of them in such a short period of time. Yamamoto also learns from Squalo, watching the videos of Squalo's battles to become Sword Emperor and learning techniques before training with the man himself.

It's not just swordsmanship either, Yamamoto starts on the baseball team even as a freshman and even had enough skills to enter the major leagues as we learn in the future arc. Even beyond baseball, he quickly picks up how to ride the motorcycles they are given during the Choice Battle against Byakuran. Yamamoto is able to do a wheelie with just a day of practice and rides it as "an extension of his arms and legs".