Tsuda Rintaro is a high school student with the capacity to predict the lifespan of living things. However, he has struggled with his abilities since he was a child, and he can only gradually observe the people around him without being able to assist them. He discovers one day that Kanzaki Umi, his childhood buddy and the one who has feelings for him, has less than 100 days to live. ~~ Adapted from the web manga series "Kimi ga Shinu Made Ato 100Nichi" (君が死ぬまであと100日) by Migihara (右腹).