Takuma, a boy who is told he will die before he's 20, and Mayu, a girl who is in love with him...After Mayu learns of Takuma's grave illness and that he will die before he turns 20, she continues to support and love Takuma. On the other hand, Takuma, who knows his days are numbered, pushes away his feelings for Mayu and distances himself from her. He cannot stand to see her cry or hurt her more than he already has. Then Mayu meets another man who has feelings for her, and Takuma meets a woman who has the same illness, and their feelings for each other begin to waver.