Takeshi Yamamoto has a warm and friendly personality and is rarely seen not smiling. Yamamoto's portrayal in the story is that of a stereotypical Japanese teenager, his looks are quite ordinary, he is a big fan of baseball, his family owns a sushi store, and later in the story, he uses a katana.
Reborn clearly sees his potential and often mentions to Tsuna that Yamamoto is a natural born hitman, mentioning as well that he is the best athlete in the entire Vongola Famiglia. His fast reflexes and athletically conditioned-body give him a natural advantage and he is shown to be able to dodge cannon fire and wayward fireworks.
Future Yamamoto has shown to have learned everything about the Mafia and seems to be okay with it. He still shows a bit of his easy-going self but has become more mature and serious. In terms of personality, Yamamoto resembles the First Vongola Rain Guardian Ugetsu Asari, something the latter acknowledges.