Human beings want to abandon their pain and achieve a state of inner peace, so they find ways to separate the pain from themselves. The painful part of me is not a human being, nor a soul, but a brand new life form. They have lives, bodies and emotions, and live on the clouds. They are called "Cloud Messengers", and the cloud where they live in groups is called "Cloud Messenger Ze".
However, the "Cloud Messengers" who were eliminated as useless parts frequently harass humans. They will continue to show humans the painful memories they have abandoned, making it impossible for them to find peace. Therefore, humans who recall painful memories are considered to have the "Sisyphus virus."
In order to completely change this situation, Executive Officer FA held a "Cloud Sky Ceremony". In name, it was to peacefully coexist with the "Cloud Envoys", but in fact, it was to eliminate them all. But he didn't know that his best friend had already crossed paths with a boy named STAR in "The Messenger of the Cloud"...