Momoka Akatsuki is the younger sister of Chika Akatsuki, sharing the family's grey hair and orange eyes. She is depicted as a teenager. Chika adores her deeply, constantly seeking her affection and attempting to dote on her. Momoka consistently rejects his attentions with indifference, often snapping phrases like "Leave me alone, you're annoying!" or "Lass mich in Ruhe, du nervst!" She prioritizes her mobile phone over interacting with him, frequently typing on it during encounters and showing minimal interest in his presence.

Their father, Yuri Akatsuki, is a cross-dressing figure who dotes on Chika, contrasting with Momoka's disengagement. During their childhood, while Yuri and Momoka were abroad, Chika was abandoned by their mother; this event shaped Chika's insecurities but shows no explicit impact on Momoka. Chika worries his undead condition might cause family rejection, though Momoka's established indifference suggests this concern remains separate from her behavior.

Momoka's narrative role is static. She appears briefly when visiting Chika at the Zombie-Loan dormitory, her fixation on her phone remaining central. No development or expanded backstory occurs. Her interactions consistently reinforce her detachment from Chika's life and struggles.