I Became the Berserker of the World I Created

A young man, struggling to support his ailing mother, continues to write unsold web novels. Then, one day, he enters a mysterious contract and finds himself transported to the world of his own creation, "The Legend of the Overlord." Not as the protagonist, but as a supporting character, Attila! In this harsh alternate world, Attila, alongside his father, Munjuk, the chieftain, overcomes his tribe's crises and distinguishes himself on numerous battlefields. Using the author's knowledge, Attila embarks on a journey to find clues to return to his home world. He leads a band of mercenaries he meets along the way, and they triumph in countless fierce battles. He ultimately faces off against the original protagonist, Charles, and his reputation soars. However, the aftermath of this encounter erodes the narrative of the novel. Will Attila ever return to his home world? And where will his epic tale end? A 100% satisfying alternate world battle fantasy depicting his growth with his companions and his struggle with destiny begins now!

(Source: Naver, translated)