The fantasy manga centers on Luce, who lives with just her younger sister after their parents died. Their true origin is from an enemy nation, and so the people of their current nation often treat them a bit badly. However, one day someone suddenly appears before Luce, with a strange request: "I want you to become my fiancé‘s lover." 育ての親を亡くし妹と二人きりで暮らすルーチェ。ある日、アセイシヤと名乗る女性から、突然『婚約者の恋人になってほしい』という予想外の依頼をされてしまう。半ば強引に連れて来られた先で待っていたのは、この国の五大家の一つ『ガイレンチェ家』の若き当主リオヴェルナだった。リオヴェルナは、ルーチェに偽装恋人の契約を迫り――？