After another sleepless night filled with gaming and losses, an unemployed young man receives a strange message on his phone: "Congratulations! You have been selected to be the King of Another Dimension." Convinced it’s either a scam or just his sleep-deprived brain playing tricks on him, he ignores the message and goes to bed. However, when he wakes up, he finds himself trapped in a slimy substance, struggling to breathe—until he realizes he’s inside an egg! Guided by Luna, a sarcastic mermaid and walking tutorial, he learns a horrifying truth: his original body is dead, and now he has been reborn as a marine creature in a new world, with the rather ambitious mission of conquering and developing an entire underwater kingdom. With no way to return home and no clue how he ended up in this absurd situation, he must survive, explore, and figure out how to transform from a mere mermaid egg into the supreme ruler of this strange new world. But does he really have what it takes to be a king… or was he only chosen because there were no better options?