'Utano Hiro,' who worked at a research institute, suddenly gets caught up in a strange phenomenon one day. When he wakes up, he finds himself in a desolate, apocalyptic world filled with horrifying "aberrant beings"! The weapon Hiro obtains is a mysterious gun called 'ES707,' which has the ability to turn back time.<br><br>To reunite with his beloved partner, 'Emma,' Hiro sets out on a journey to travel back in time using this gun!<br><br>Encountering various survivors in the post-apocalyptic world, repeatedly turning back time, and facing relentless battles, Hiro gradually uncovers the mysteries of this ruined world...<br><br>What exactly happened to the world? Can 'Hiro' safely reach the origin of everything, 'DAY 0'?!