Yukinari Arima is a member of Shishitoren.

Arima is a tall teenager with messy brown hair that is lopsided to the right side of his face, while leaving his left side shaved, while sporting rough expressions. He dons the Shishitoren jacket over a white shirt.

Arima is an arrogant, smug and violent teenager, reflecting the infamous stereotype of Shishitoren. A notable bully, he has no qualms about chasing a middle schooler on their turf as sport all the while ridiculing his teammate who got beaten. Provocative and underhanded, Arima has no qualms about playing dirty in order to win. He is shown to be quite observant as he instantly deduced Sugishita's devotion towards Umemiya and utilized it, in order to distract him. In despite of his cruelty, Arima genuinely cares for Kanuma, with the two being close friends.