After Kiryu's sudden withrawal to the world of sports, he lives his life in high school to experience the youth that everyone does but before that event happens, it is followed by another event. As Kiryu is given an envelope with no letter inside his shoelocker, he is met by countless letters that belongs to someone and with all of the sudden mysteries that was coming, he tries to solve them all while understanding and learning the youth. And now, his Youth Romantic Comedy life starts.