The protagonist, who has difficulty falling asleep, falls asleep every night with the help of sleeping pills and embarks on a fantasy adventure of fighting zombies and monsters.
The setting in the first chapter is that the protagonist can control his own dreams as the dream progresses, and is basically invincible. The setting is changed in the next two chapters. If the protagonist dies in the dream, he will die in reality. The alarm clock is a prop. When the time is up, the protagonist can return to reality if he is not dead in the dream and activates the prop.