Daisuke Matsuo is Miharu Takeshita's boyfriend and a student at a nearby college. He makes sporadic appearances, primarily providing Takashi Kosuda with pragmatic relationship advice concerning Kosuda's interactions with Yamada. His composed and insightful suggestions originate not from personal intuition, but from previously hearing details about their relationship through Miharu. This positions him as an indirect conduit channeling Miharu's observations rather than acting as an independent advisor.

He first appears in Episode 2 during a pool outing, where Miharu briefly worries Yamada might pursue him. Instead, Matsuo and Kosuda quickly become friends. In this episode, he suggests Kosuda hug Yamada during a fireworks display to resolve a misunderstanding – advice Kosuda successfully follows. This establishes his role in facilitating minor developments within Kosuda and Yamada's relationship through practical, Miharu-informed suggestions. His involvement remains confined to these supporting appearances focused solely on advising Kosuda based on secondhand information.