Mikawa's Takanobu Nishikawa scored a season-best 18 points on 7-for-10 shooting on Friday night.
The SeaHorses also dominated on the boards in an 84-77 victory over the visiting Levanga Hokkaido.
Isaac Butts, J.R. Sakuragi and Ko Kumagai added 15 points apiece for the SeaHorses (15-15) in Kariya, Aichi Prefecture.