Miya Shiba

As the twin sister of the Yotsuba clan's current leader, Maya, this influential figure serves as the mother to both Tatsuya and Miyuki. Although she remains a central part of the family's complex history, her life was tragically cut short by failing health before the main events of the series unfold. Her presence is primarily felt through flashbacks, specifically during the Reminiscence Chapter set in 2092, shortly before the central timeline begins.