Byaku and Matsudo

Heisuke, along with Kagumi, corners Byaku. It is revealed that Kagumi was Byaku's dead wife and that Byaku, though no apparent, is actually nine years older than Heisuke. Several flashback scenes occur as Byaku and Heisuke chat and fight (Kagumi does all the fighting for Heisuke). Byaku performed experiments on his wife and in the end she died.

Synopsis excerpt via Kitsu.