What would happen if Kazuya died on the day that Mami broke up with him? He choked on instant noodles and died alone in his apartment.

A college student who was partying with his friends got alcohol poisoning and died.

The soul of that college student takes over Kazuya's body and inherits a scant few memories of that guy along with a system.

A system that would support him in his journey to do whatever he wants.