Hana Nusubito wa Shounen no Uchi

Riko, a young lady who grew up in an adult world full of calculations, suddenly finds herself living at her cousin Masami's house after the death of her parents.

Despite the drastic change in her environment, Riko finds a little happiness in living with Masami, whom she has admired for a long time, but there is another boy living in the house - Asagi, who is not related to her by blood.

Riko is annoyed by Asagi, who is cheeky, impudent, and outspoken despite being younger than her, but on the other hand, she is moved by Asagi's honesty.