Counterattack System appeared when I'm already At The Mahayana Realm - Chapter 728 - 727: Taiyi Seal

His Royal Highness the King of Han, who was afraid of the dark and ghosts and loved to cry, has always been the good baby of the princess.
Until one day, His Royal Highness the King of Han found a book in the bookstore…
Picture book?
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Search keyword: Protagonist: King of Han, Princess of Han

- Description from novelbuddy

Sano Yuji, a black company employee, is summoned to another world while finishing his work at home. His profession in the other world, a Monster Tamer, is considered a job that makes it difficult to become an adventurer. However, thanks to some slimes he met, which read several magical books, he gained magical powers and the second profession, Sage. Yuji acquired overwhelming power, but is he conscious of his strength? Blindly becoming unparalleled and strongest in the world!

Daytime belongs to the human world, while Deceit Night returns to the netherworld.Since the arrival of the sinister night, demons and evil spirits have brought disaster to humanity, and generations of our ancestors have struggled to survive.This blade of mine can eliminate evil, slay demons, defeat wickedness, exterminate devils, destroy evil!From now on, nighttime shall be like daytime!