Minami-kun ga Koibito?!

Chiyomi, is a high school girl who was born and raised in a retro Showa-era shopping district in Shonan. She is a member of the basketball club and has a kind personality that stays cheerful despite her somewhat complicated family structure. She and Minami-kun, also known as Minami Hiroyuki, a basketball star from her hometown of Shonan, have been like siblings since childhood, and they are happily in a relationship. However, one day, he suddenly becomes 15cm in size and fits in the palm of her hand. Chiyomi begins living with him in his now tiny body.