One of Kae's classmates. He is very popular and reliable, and is part of the football club. He can be characterized as "the boy next door" type. Igarashi is often paired with Nanashima by Kae, who strongly supports their interactions and intimacy. His name is written with the character for "5", thus he is the "5" in Kae's ship name for him and Nanashima: 5x7.
When Kae becomes chubby again, he realizes that he likes Kae even if she isn't super pretty.
As of chapter 27, Yuusuke has kissed Nanashima twice.
He had a senpai named Kotoha whom he used like. He choose Kae over Kotoha.
