Chuugakusei ga Toshiue ni Koi Shicha Dame Desu ka?

Inori is a college student who had a fear of men due to a traumatic experience. When Inori got into trouble one day, she was rescued by Riku, a junior high school student. Inori thought that it was cute for little Riku to want to act like an adult, but Riku has fallen seriously in love with Inori. However, Inori's younger sister, Kasumi, also has a crush on Riku...? (Source: B Komi, translated)