As middle school graduation approaches, Ryou Karuizawa finds himself burdened by one thing: his unspoken love for Miton Omoi. With her stunning looks, impressive academic record, and wonderful personality, Omoi is an all-around catch, but even when she announces plans to attend an all-girls high school, Karuizawa decides to bare his heart and confess anyway. To his surprise, Omoi happily accepts his feelings, leaving Karuizawa in a daze about what's to come. Meanwhile, Omoi doesn't waste any time in planning their future together, including transferring to Karuizawa's school, setting absurd relationship rules, and even deciding on a wedding date two years from now. Karuizawa realizes that Omoi's feelings are as weighty as her name suggests: unbelievably heavy!