In a flashback, Professor Nemuro is an 18-year-old prodigy who, in spite of his intelligence, feels no emotions for anyone or anything. He is hired by Ohtori Academy to lead a research team of 100 boys to discover the secret of eternity. When he becomes close to his supervisor Tokiko and her terminally-ill brother Mamiya, Nemuro finally feels the value of human life and throws himself enthusiastically into his research, but events orchestrated by the End of the World destroy everything he believes in and lead him to become Mikage.