My sister-in-law was cuckolded ~ I'll do it in place of my big brother! ~

It's been three years since I got married. Yui is a wife who is very grateful for her husband, who has collapsed from a sudden illness. Koji, the brother-in-law who secretly admires Yui, is also worried about the future of the two, but there is nothing they can do... One day, as usual, Koji visits and encounters Yui's sexual desires being processed. Koji sneaks around, as if enchanted. Furthermore, due to the loneliness that prevented her from having sex with her husband, Yui was comforting herself alone in the room. Koji can't control the lust that surrounds himself...