Once upon a time, she was my cute little sister who would say things like, 'When I grow up, I'm going to marry you, big brother!' But lately, Kotone has been avoiding me. Well, I guess it's probably just her being tsundere. There's no way Kotone could hate me. She seems to be in a good mood on the phone with someone... Could she have a boyfriend now!? Before my beloved sister falls into the hands of some unknown guy, let me be her first partner. Let's graduate from being a virgin together.
