Hatano's the smallest guy in D Agency, which he's definitely aware of. He comes across as pretty friendly on the surface, but there's a real pride underneath—he's not someone who takes things lightly. He's got that cocky streak that makes him rub people the wrong way sometimes.
What sets him apart is how agile he is. He's a genuinely skilled martial artist, one of the best in the group, and he knows it. That confidence (or cockiness, depending on who you ask) probably comes from actually being able to back it up in a fight.
Content compiled by AnimeList.moe from publicly available sources.
