A multi-story, multi-ending love adventure game based on Shin Takahashi's original manga. The player becomes the main character, Shuji, and experiences the last love on earth with the ultimate weapon, Chise.

The purpose of the game is to keep Chise in a happy state and continue to fall in love with her until the last day on earth. Depending on the player's choices and actions, "Chise"'s "happiness value" changes, and "Chise" becomes an existence more than "she" or more than "weapon".