Sister NTR: My sister, who loves me, cheated on me (HBAD-505)

Mamiko lives in her older sister Kanna's apartment in Tokyo while attending university. Kanna and Mamiko's boyfriend, Takashi, are also good friends. Although Kanna appears to be spying on them, she is actually targeting Takashi. She then sets a trap for him, asking him to cater to her sexual desires, but Takashi can no longer bear the guilt he feels towards Mamiko…