Yuuya Kanzaki

Mitsuki's stepbrother. An average Japanese high school student, Yuya's goal is to have a fine sibling relationship with his new little sister. He is generally good-hearted, but because he grew up without a mother and little companionship with females, he has an incredibly poor ability to understand and empathize with Mitsuki's feelings. He also has a tendency to make very inaccurate assumptions based on unusual circumstances, and despite his good intentions, his attempts to help Mitsuki often cause things to become worse, such as when she needed to go to the washroom, and he assumed she was sick and forcefully dragged her to the school clinic despite her protests. Due to his misunderstanding about Mitsuki's chastity belt and Hiyori, he believes that Mitsuki and Hiyori are a "lesbian cosplay couple".