Yuuya Masaoka, nicknamed "Yūya," is a flashy, self-assured friend of Natsuo Fujii, embodying a playboy charm that masks his disciplined academic pursuits. Though committed to a girlfriend, he indulges in flirtations with other women, regularly joining group dates and lively social events. This carefree persona contrasts with his enrollment in a preparatory school, hinting at an underlying focus on his studies.

A concealed chapter of his past involves a physical relationship with Momo Kashiwabara, a classmate of Natsuo and Rui. Their discreet history subtly colors his interactions within their social circle, remaining initially hidden. Momo’s own reputation for casual relationships, alongside her academically driven yet tumultuous personal life marked by family strife, further defines the intricate tension between them.