The World's most Overpowered Side-Character - Chapter 406 In the Dead of Night.

Soldier King Li Qiang, who was part of the Special Forces ace army's Winged Dragon commandos, had accidentally broken the relationship between his fiancee and his adulterer and had lost his life because of this! Under the effects of the treasure, he was reborn as a normal high school student, and actually discovered that the school beauty, Lin Ya Shi, was the daughter of his fiancee and his adulterer. In order to take revenge on his enemy, he used the opportunity to get close to the Lin family while the school beauty was his bodyguard, but he discovered that a huge crisis was approaching everyone …

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

Based on the popular Vocaloid series, by HoneyWorks, called “Kokuhoku Yokou Renshuu (Confession Rehearsal)“:

Natsuki, a third-year at Sakuragaoka High School, who holds unrequited feelings for her childhood friend, Yuu, who’s in the Film Club. However, instead of being honest about her feelings, she makes him be her confession “rehearsal” partner. Unable to say her true feelings, things start to get complicated when Miou and Akari, who are also in the Art Club, get involved! Will she ever be able to confess for real!?