When you were just seven years old, a summer vacation on a remote Japanese island led to a promise—a promise to marry a girl someday. But life in the bustling city pulled you away. Now, as a high school student with a heart set on the class president, your life seems promising. However, that distant promise catches up with you when the island beauty transfers to your school and announces herself as your fiancée! Your peaceful high school life is thrown into chaos, and you're torn between your past and your heart. Having a fiancée doesn't seem to deter your best friend and crush. If anything, their obvious jealousy brings them closer to you than ever. With all three girls vying for your attention, will you honor your childhood promise or let your heart decide your destiny?