Kozoumaru is a short, overweight boy with tanned skin and spiky, dark purple hair that is grey around his temples. He has sharp black eyes, thin eyebrows and a small, pointy nose.
His casual wear consists of a white shirt under a red jacket with white buttons, dark blue shorts and white shoes.
Kozoumaru is first seen during episode 1 watching from the school as the other Inakuni soccer club's members practiced outside. Later, while Asuto was trying to convince the other Inakuni members to go to Tokyo and play in the Football Frontier against Seishou Gakuen, he reappears and interrupts him, stating that the team is acting as if they already lost.
He explains that he traveled to Inakunijima for special training and wonders if a bunch of cowards like them could do anything, angering Goujin. He goes further, saying that a bunch of chumps already scared before a match would have no chance to win at the Football Frontier. Goujin tries to argument they might be able to win one or two matches if they try hard enough, but Kozoumaru calmly states that the Football Frontier is where Japan's best team is decided and, from the get go, the committee will ask weak schools to withdraw before even trying. Moreover, he claims a team without a single Hissatsu Technique like the Inakuni would have no chance at all and that they'd be better finding another hobby besides soccer. He is slightly surprised when Asuto says he is going to do it anyway.
- Kozoumaru's birthday is on July 14.
- In Inazuma Eleven Ares no Tenbin manga he's the first player to get a yellow card