An Upbeat Kind of Guy

Yamamoto Takeshi is percieved as an outgoing and carefree sort of guy by his friends because he's always smiling and laughing. To an extent this is true, the Yamamoto they initially meet just wants to have fun with his friends and play baseball. This is just the face he presents to the outside world however because when it comes down to it he is competitive, loyal, and takes the things he cares about very seriously.

Yamamoto first appears in Chapter 5 as popular jock at Tsuna's school. The other students jokingly call him "baseball freak" because of his obsession with the sport. He's talented as shown by his placement as a starter on the team even as a first year student. When Yamamoto ends up injuring himself by overtraining he tries to jump off the room of the school because without baseball he feels his life means nothing. While Tsuna is able to talk him out of it, this single moment defines who Yamamoto Takeshi is. A guy who despite an easygoing exterior, puts 100% into everything he does and his unwilling to accept failure.

Yamamoto commits himself to Tsuna's friendship after Tsuna convinces him not to jump. After that moment he can often be seen hanging out with Tsuna and the gang. As a member of the baseball team and a generally amicable guy, Yamamoto is quite popular with his classmates. Yamamoto doesn't care about that, though. Even before Tsuna saves him he's willing to have Tsuna on his team in gym class and even asks his advice when most of the other students would ignore "No Good" Tsuna. He continues to foster a friendship without concern for his own social standing and by the time Tsuna and his friends find themselves fighting genuine threats Yamamoto is wholely committed to helping Tsuna, even learning his father's sword technique to do so.

Yamamoto is often mocked by Gokudera for not taking the events around them seriously. In fact Yamamoto repeatedly calls it a "mafia game" and gives the impression that none of the events around him are real and instead it's all an elaborate game. He's committed to that lie because it's something that he uses so that he can continue to smile even in life or death situations. Despite that, the deadly serious look in his eyes every time he enters battle and the injuries he sustains while fighting tell a different story. Even if he realizes it's real he never says as much in order to help his friends sustain an air of normalcy.