Eishin graduates high school on his 18th birthday. He decides he was going to confess to the girl of his dreams. When he decided to confess to her, he accidentally ended up confessing his feelings to HER. During the confession, a bomb goes off at a cookie plant, which causes the world to be eradicated. He passes out and wakes up next to a gate. Play the rest to watch the story unfold.
Disregard the price tag, the game is currently free and there is a web browser version too.