Kangetsu Mizushima, a former pupil of Sensei Kushami, now advances his doctoral studies in physics at Tokyo Imperial University. His name, meaning "wintry moon," hints at a reflective and somewhat detached nature. He possesses a noticeable gap in his front teeth and is habitually clad in a black cotton haori jacket that seems too small for his frame.

He frequents Kushami's home, where his conversations persistently revolve around women and boast of multiple romantic exploits, revealing a deep-seated interest in courtship. His primary narrative focus is his tentative pursuit of Tomiko Kaneda, the spoiled and haughty daughter of a wealthy businessman. Kangetsu's indecision over this potential marriage becomes a frequent topic among Kushami's associates. His interactions within this circle, including with the garrulous Meitei, define his social role. He engages in the group's philosophical and cultural debates while his personal arc remains tied to his academic career and the unresolved romantic subplot involving the Kaneda family. His attire, blending traditional haori with scholarly identity, embodies the cultural tensions of the Meiji period setting.