Meet Sasaki, an overworked, middle-aged office worker. His days are marked only by the passing of more unrewarding corporate drudgery. Smoking helps take the edge off, but other than that, the only bright spot of his day is when he goes to the nearby supermarket and sees Yamada's smiling face. So, one evening after yet another exhausting day, he heads to the supermarket to find he missed Yamada's shift. Dejected, he decides to go find a smoking area but discovers there isn’t one to be found. Just as he’s about to leave, a girl in a biker jacket named Tayama asks him to join her at a secret smoking area!

Ryūsei Narukami is your typical NEET. He spends his days shut in his room playing video games without a care in the world, living a lazy life. But the truth is, Ryūsei used to be a powerful demon king in another world! So why not spend this new life doing whatever he wants? Except, he wasn't the only one reincarnated into this world. The hero who struck him down is here too—and she's a really cute high school girl?! Can Ryūsei survive reuniting with his foe in a new world, or will he find himself fighting even in this life?