Seichi is a fat, ugly high schooler who lives a boring life of getting bullied, However, one day all that changes. A mysterious voice suddenly rings out over the school's PA system and sends them all to another world!
After Seiichi defeats a gorilla-like monster, a Kaiser Kong, she proposes to him. The gorilla named Saria starts her new life together with Seiichi. While she is kind, innocent, and forthright, he still plans his escape from her since she's a gorilla.
When Seiichi rescues Artoria, she's on the verge of death, so he faces the Black Dragon God himself! Though the frightening strength of the Black Dragon God poses a challenge, he manages to defeat it.
Seiichi's attempts to cheer up Artoria somehow come out as a proposal. While their relationship grows awkward, Seiichi and Saria pass their tests and successfully join the adventurer's guild.
After eating the Fruit of Evolution, the donkey Lulune evolves into a beautiful woman! Seiichi's harem just keeps growing but shortly after a brigade of female knights, the Valkyries, takes Seiichi into the royal castle. What awaits him there is the beautiful brigade captain, Louise. She suddenly challenges Seiichi to a duel, but how does he fare. And what is the sad past that Louise hides?
The identity of the assassin who attacked the King. is a young girl, Oliga. Seiichi stops her attack, however, the king falls into a coma thanks to a curse. Can Seiichi save the King?
Seiichi fortunately manages to save Oliga, and after learning of her tragic past, Seiichi frees her from her cursed destiny and feels intense anger toward the Kaiser Empire that was behind it.
Barnabus, the mage known as the "Transcendent", comes to Wimberg Kingdom. He is also the principal of the Barbador Magic Academy that Kannazuki and the others attended. Barnabus claims that a problem has arisen with the arrival of heroes from another world. Then an urgent messenger appears with news that a large horde of monsters has appeared in the woods near the kingdom.
After witnessing his abnormal power, Barnabus invites Seiichi to become an instructor at Barbador Magic Academy. Seiichi accepts, believing it will allow him to see Kannazuki and the others. However, that means bidding farewell to the Wimberg Kingdom. With his remaining time there, Seiichi comes up with an idea--taking Saria, Artoria, Lulune, and Oliga out on dates!
