Books like tales of demons and gods

The Gamer (Korean: 더 게이머, RR: Deo Geimeo) is a webtoon hosted by Naver Webtoon. The webtoon is loosely influenced by fantasy RPGs, Dungeons & Dragons, and comic fantasy book series Discworld but set in contemporary South Korea, originally not introducing anything out of the ordinary. Once the main protagonist, Han Jihan, notices a dialogue box in front of him like in a video game, he recognizes that he has become a video game character, and supernatural events start happening.

Han Ji-Han was a normal high school student who developed a special ability that allowed him to treat the world around him as a game called 'The Gamer'. He noticed that by leveling up, he could increase his stats and improve his body and mind, among other things. The day after noticing that he can also increase his stats through training (he studied to increase his Intelligence), he accidentally slipped into a combat area for those who have a link to the Abyss, the hidden world of their own. He witnessed a battle between Kwon Si-Yeon and Hwan Seong-Gon, getting involved in it as well. He was approached by Kwon Si-Yeon, who questioned him on his identity.