Overbearing Tyrant is a Manga/Manhwa/Manhua in (English/Raw) language, Action series, english chapters have been translated and you can read them here. You are reading Overbearing Tyrant chapters on https://mangabtt.com, fastest updating comic site. The Summary is
In the year 202X, the Otherworlders invaded Earth. The otherworlders have more sophisticated technology and hunted down humans with combat robots and viral weapons, and the remaining humans battled on for 10 years just to survive. The main character, ‘Park Sung Hyun’, was the leader of the troops in Incheon, Bupyeong. Prior to the invasion of the Otherworlders, he used to be a part-timer at a convenience store like an ordinary person, but he became a strong warrior in the process of losing his family and battling to avenge them. In the midst of the attack against the Otherworlders’ headquarters, Park Hyun Sung got trapped in a warp portal with the leader. When he woke up, he found himself in a fantasy world that reminded him of the medieval times in Europe, and his soul was trapped inside a weak blonde 15-year-old pretty boy’s body. Hyun Sung was surprised by the unfamiliar surroundings and his weak body and found out that he is occupying the body of Ian Albarren, and that his father is the lord of a land who owes a large debt to the great lord and faces a difficult time ruling over his land. Park Hyun Sung, who had been fighting against combat robots and viral weaponry from the Otherworlders who had advanced scientific technology, decides to get used to this fantasy world to fight against monsters with armor and swords.