Humans are extinct, only computer "CZ 25" with a will keeps existing. He strongly wished to see his creator and other human beings, and one day the goddess of time comes before him. She decides to change the past in order to fulfill his wish.
Modern time. Takuya Saito fell ill on the day of exams and now he is a ronin. One day Takuya is inspired by old friend Hiroyuki to become a high school graduate. What fate awaits Takuya?

[From vndbreview]