Yūya Tenjō, un niño que ha sido severamente acosado desde la infancia. Lo que encontró en la desesperación fue la 'puerta a otro mundo'. Arma de clase trampa. monstruo diabólico. Yūya está desconcertado por la situación similar a un juego de fantasía, pero cuando regresa al mundo real, la subida de nivel en el otro mundo comienza a afectarlo... ¡La fantasía de inversión de la vida ahora comienza!

When Yuuya reunites with the girl he saved back at the convenience store, she invites him to attend the prestigious Ousei Academy. Yuuya isn’t sure that he’s worthy of attending a school full of geniuses, but he’s persuaded to try it for just one day.

Yuuya realizes that he doesn’t have many clothes that fit his new, leveled-up height. So, he heads to the mall where, in an unexpected turn of events, he ends up participating in a fashion photoshoot opposite a super popular female model?!

Yuya responds to Princess Lexia's marriage proposal and receives an invitation to an audience at the royal palace. At the same time, he returned to the Ôsei Academy.

As Yuuya tries to find a way to level up in the Darkest Regions, he comes across a Black Fenrir pup. Yuuya Tames him, names him Night, and brings him home to live together as family. Side by side, they explore the Darkest Regions...and also go for walks.

Yuuya has found The Book of the Sage. As he reads it, he realizes that it’s even more amazing than it seems. Meanwhile, the class’s study trip draws near. Yuuya is at the department store with his friends to buy supplies when trouble suddenly strikes.

Yuuya runs across a girl fighting monsters in the Darkest Regions. She calls herself Luna. They begin spending their days training together, sweating side by side. Back at Ousei Academy, the off-campus study trip begins at a site deep in the mountains.

The study trip isn’t at all what Yuuya and the others had imagined. They’re faced with a series of unexpected challenges. Later, Yuuya meets with Lexia and her guards so they can escort him to his audience with the king, but Night begins acting strangely.

Lexia has been attacked, a crime punishable by execution. But Yuuya knows the would-be assassin and he can’t help wondering what could have caused them to do such a thing. The answer is shocking...as is the arrival of a new family member for Yuuya.

Yuuya gets an offer to join the entertainment industry. His friends are stunned to learn that he’s already had a brush with that life. In the other world, Yuuya’s leveling up plateaus and he wonders if he’ll be able to get any stronger on his own.

The Director still has designs on Yuuya, but he's too busy studying for his upcoming exams to worry about it. Kaori comes over to help him with math, and then...! Later, Yuuya takes advantage of a short school holiday to head for the royal capital.

Lexia is determined to make the most of Yuuya's visit to the capital in spite of everything that's happened. When Luna and Lexia take Yuuya out of the castle to show him around town, the signboard of a certain guild catches his eye.

Reigar has been captured and must pay the price for his crimes, but Yuuya still has to deal with the enemy girl who proved to be just as strong as he is.