It's Not Easy Being Your Love Rival's Big Brother - Chapter 29

The protagonist, a famous YouTuber known for playing the game trilogy “Tril Trilo Trilogy,” finds himself possessing the final boss of the game world.Before the release of the new instalment in the series, he receives an offer from the game’s developer to play a prequel, “Part 0,” which explores events that occurred before the first instalment. Since he is a fan of “Tril Trilo Trilogy,” he eagerly accepts the offer.However, through some twist of fate, he wake ups in the world of “Tril Trilo” in the dreadful body of the final boss of the trilogy, a character named Frank Wonderstein.

In the current era, people are either normal or are with ‘special abilities’. Cases related to the latter are managed by the “National Anomaly Prevention and Control and Special Species Management Office”.
Qi Zheng Emperor Sheng Lingyuan was reawakened a thousand years later after he jumped off the fiery Red Lake. Xuan Ji, a newly transferred staff to the Reparations Division of the Deviant Control Office, finds himself having to clean up the mess of a revived tyrannical monarch. The two seemed to share something from the past, but unbeknownst to them, a big conspiracy is stirring right underneath their noses that could destroy the balance of the world.

- Description from Novelupdates

When our protagonist becomes the game character Jun Karentia, she thinks she has it made. She may be just a lowly support mage, but with her knowledge of the game, she knows she can finagle her way to the good ending following around the main character, Fabian. The problem? This game doesn’t end after one playthrough. Jun is prepared to guide Fabian through the second playthrough to the true ending when… Fabian abandons her. Now the Grand Duke Mayer Knox—captain of the Dark Knights and the secret final boss—is determined to have her join his party. Can Jun turn the final boss into the main character? Why is Mayer Knox so intent on having her in his party? And when will these rumors about being his lover stop?!