Mashū Kirinoe is a supporting character from the anime Opus.COLORs, a student in the grader specialization of the Perception Art department. He is described as a perfectionist with a ruthless and cold demeanor, earning him the nickname "the monster of the grader course" from his peers. Among grader students, he is both feared and respected for his uncompromising standards and intense approach to his work. His personality is a key factor in escalating the traditional conflict between artists and graders known as the Artist vs Grader War.

Kirinoe's most defining relationship is with his childhood friend Kaede Mikuriya, whom he treats as a sworn enemy. Their mutual antagonism is deep-rooted and volatile; whenever Kaede is involved, Kirinoe becomes completely unmanageable. Only two other childhood friends, Yuichi and Kohei, are able to intervene in their fights, though even they cannot resolve the fundamental hostility between them. Aside from Yuichi and Kohei, his only close companion is a rabbit named Usako.

In terms of appearance, Kirinoe is a male adult with short brown hair and green eyes. His role in the story is that of a formidable grader who contributes to the ongoing tensions within the Perception Art program. Beyond his combative relationship with Kaede, information about his personal background, deeper motivations, character development over the series, or any special abilities beyond his grader skills is not detailed in the available material.