When we first meet Yamucha, in the first few episodes of Dragon Ball, he is a mischievous bandit roaming the deserts for hapless victims. He is also absolutely terrified by any member of the opposite sex that is approximately his peer, and is rendered completely petrified just by making eye contact.

Eventually, after first being Goku's enemy, Yamucha winds up being thrown into the fight against Pilaf to collect the Dragon Balls. First, he seeks the seven spheres for his own use- to wish upon Shenlon not to be so painfully frightened of girls. However, his wish was never granted directly. Instead, he remained with the emerging Z-Senshi, and over time grew used to Bulma's presence.

Yamucha quickly recovered from his female-phobia, but he never lost that boyish charm and devil-may-care perspective he gained from roaming the world on his own as a child. He is very pleasant by nature, and honestly prefers a quiet, normal life over the death-dealing adventures his allies participate in through Dragon Ball Z. He even becomes a professional baseball player (and is the only Z-Senshi who actually has a paying job!). As one of the weaker Z-Senshi, he is unable to make much of a contribution once the Saiyans arrive, but he remains on board as a close friend of the team, and Bulma's sweetheart. However, while that relationship eventually fizzles, he remains close friends with all.