On Oriyama Karin’s 16th birthday, she receives a present from her parents. Her present is marriage. The person she marries is her first love Tsurugi Nao. He is a popular senior in high school. For Nao, he only marries Karin for economic reasons and in particular the wealth of her parents. Karin loves him truly, but Nao doesn't love her at all.
Their marriage is a secret, but Ebina Isuzu, who holds read morefeelings for Karin, learns of their marriage.