Hitsuji is a spoiled and cute little brother who needs a lot of care. Coupled with Aimi's caring nature, she has continued to take care of everyone since she was a child, even now that she has entered the workforce. However, Hitsuji is not her real brother, but a younger boy who is her childhood friend. She's worried about him, can't leave him alone when he begs for her, and even starts living with him, but Hitsuji is just like a younger brother to her and not a love interest! In fact, Aimi recently found a marriage candidate who's a good man. But when Hitsuji found out about it, suddenly...!?