Inran Onee-san to Himitsu no Sankaku Kankei

Shinichi is a young man who finds himself caught in a complicated relationship with his older neighbor, a seductive woman named Misaki. Their secret encounters begin when Misaki takes an interest in him, leading to a series of intimate and taboo moments behind closed doors. As their connection deepens, Shinichi struggles to keep their affair hidden from those around him.

However, the situation becomes even more tangled when Misaki's younger sister, Yui, discovers their secret. Yui, who has her own hidden feelings for Shinichi, decides to insert herself into their dynamic, creating a tense and erotic love triangle. With both sisters vying for his attention, Shinichi must navigate the dangerous waters of desire, jealousy, and forbidden relationships.