High school student Kudo Akira discovers he possesses the unexpected ability to travel freely between modern-day Japan and the fantastical world of Do-Melta. Unlike many who find themselves in another world, Kudo is not burdened by a grand mission, a call to defeat a demon lord, or any pressing duty. Instead, he uses this power purely for leisure and personal enjoyment, spending his after-school hours exploring a massive dungeon located at the center of Do-Melta and focusing on leveling up at his own pace.

The story follows Kudo as he navigates the low-stakes but often troublesome social dynamics of his dual life. In Do-Melta, he registers as an adventurer and interacts with a colorful cast of characters, including a cunning guild receptionist who frequently tries to mooch off him and his magic instructor, Beitreise, who has a habit of offering questionable rewards. Despite his protests of hating pain, disregarding rank-ups, and finding guild requests troublesome, Kudo continues to get dragged into various situations, including forming bonds with the people he helps, such as a girl he rescues early in his journey.

The narrative unfolds across several laid-back adventure arcs. In one notable storyline, Kudo invites his friend Scrael, a Long-Ears, to visit his home world of Japan. He later repeats the invitation for Eldrid, a Tail girl, but trouble arises when he loses sight of her at an amusement park, forcing him to locate his friend and safely return her to Do-Melta. Another arc involves Kudo wandering through Do-Melta only to be kidnapped once again by his mentor Beitreise, who takes him to an undiscovered route leading to hot springs, presenting a new and embarrassing challenge. As the series progresses, some of the mysteries surrounding Kudo's personal life also begin to surface, adding a new layer to his otherwise relaxed otherworldly excursions.