Mio is a hard working girl who happens to come from a poor family. She lives with her brother Hina(ta) and because her mother is hospitalized and her father dead,is forced to do a number of part-time jobs to pay for rent and living expenses. But things get even more complex for her when she encounters Shoei who then steals her first kiss and then offers to 'buy her'.
The next day, Mio's mother tells her that their landlord has offered her a job working as a maid for them. She is reluctant but still goes to see him about the offer. To her surprise, she discovers that the man who stole her first kiss the night before is the landlords son and the high-achieving student at her high school commonly known as Prince Jinnai.
She later discovers a secret connecting Shoei and her during her childhood, and the reason why she has no memory of ever having any friendship with him.