Chisa Aso engages in a sexual relationship with Akira Amemiya's sister, established through narrative implication. She fixates on Akira primarily because he physically resembles his sister and due to details about him shared by the sister. Chisa treats Akira as a plaything, objectifying him within her self-absorbed world and disregarding his feelings entirely. Akira, in turn, openly despises her, reacting to her intimate connection with his sister and her dismissive, manipulative behavior towards him.