HBAD-505 Sister NTR I was cuckolded by my sister who loved me

Mamiko lives in her older sister Kanna's apartment in Tokyo to attend university. - Kanna is also good friends with Mamiko's boyfriend Takashi, and although it seemed like she was watching over them, she was secretly targeting Takashi. - He then sets Takashi in a "trap" and calls him in to take care of his sexual desires, but Takashi can no longer bear the guilt he feels towards Mamiko...