Due to being overweight, Yuuya has been discriminated and harassed all his life, even by his own parents and younger siblings.
Starting middle school, his life has taken a turn for the worse, however, despite everything, thanks to his grandfather support, Yuuya has endured the humiliation, knowing that he will always be on his side.
But one day, his grandfather loses his life, leaving him as the sole heir to his house and assets. Immediately, Yuuya’s parents try to strip him of the inheritance, but luckily for him, his grandfather anticipated their actions and left them empty-handed.
Frustrated, Yuuya’s parents abandon him to his fate, with no desire to see him again.
One night, as Yuuya returns home, he sees three men harassing a young girl, Kaori, and remembers the kind words his grandfather shared with him. And despite his fear, Yuuya tries to prevent the girl from being harmed.
Yuuya ends up beaten, but without asking for anything in return he returns home and avoids getting involved with Kaori or the authorities.
Now, Yuuya struggles to graduate middle school, works to support himself, and tries to avoid trouble. But his classmates don’t stop looking for him to terrorize him, and on graduation day he receives a beating, while in the distance his younger brother and sister enjoy it.
Returning home, despair seizes Yuuya and he breaks a mirror with his fist. As he hits the wall again, something happens and a door opens, directing him to a room full of objects.
Yuuya remembers that his grandfather used to travel and collect rare things, and suddenly he sees a second door. Opening it, he enters another world, which immediately gives him a series of titles, just like in video games.
It doesn’t take long for him to understand what’s going on, and he receives ownership of a house and several plots of land around it. He finds different types of weapons and it is enough for him to take them in his hands to gain control over them.
Going out to practice, he learns that only he can enter the property, but that doesn’t stop various monsters from trying to do so. And when a huge ogre appears, he somehow loses its life with a single attack from Yuuya.
Inadvertently, while he remains in the other world, Yuuya’s physical appearance transforms, he grows up and loses weight rapidly.
Finally, the day has come when he must return to begin high school, and the first day no one believes that he is the same Yuuya that everyone teased, even his own siblings demand to know what has happened to him.
At that moment, Kaori gets out of a luxurious car and asks directly for Yuuya.