Sumire, an introvert otaku, has a step-brother after her mother remarries, and they end up living together. Sumire can't help but dote on her first step-brother and find him cute. Sumire, a secret nerd who can't control her feelings for her brother-in-law, dotes on him with a unique creepy way of speaking, whispering lewd things. Her love for her brother-in-law, which she cannot refuse, goes out of control and escalates!
