Akuyaku Reijou ni Nanka Narimasen. Watashi wa『Futsuu』no Koushaku Reijou desu! - Chapter 169.2: Serious match.

Arakawa Kouki is reincarnated to a Japan with a different history than the Japan he knows with the memories of his previous life still intact. Kouki was discouraged, “Aren’t reincarnation stories supposed to be at some fantasy world filled with swords, magic and elves?!”

Marcella Valemont was a villainess wrapped in silk and thorns.The alluring, selfish daughter of the High Priest, she was forced into a cold marriage with the Black-bellied Duke Berith Montclair. She longed for power and would stop at nothing to claim the crown, even if it meant seducing the incorruptible Crown Prince Lucian and clawing her way to the throne into becoming the Queen.Until it all burned.Her ruthless schemes led to betrayal, rebellion, and ruin-- an empire on its knees, a virtuous king destroyed, and a rebellion led by the man she discarded. Desperate and full of regret, she barters her life with the Duke to save Lucian.In an interesting turn of events, Marcella gets to go back in time to fix her wrongs, save the man who was ruined because of her and hopefully stop the bloodthirsty rebel Duke Berith.She finds herself reborn as her 18-year-old self with a chance for a do-over and vows to do better this time.But the past does not forget. Nor does the devil in her husband’s skin.Secrets long buried begin to surface, and Marcella discovers that her former husband is far more than he seems—a man cloaked in darkness, harboring a purpose that threatens everything she holds dear.They say second chances come with thorns and to fix the past, she must trust the devil who destroyed it.

Cosplayer Liu Mang accidentally crosses through time and arrived at the Eastern Han Dynasty wearing Aries Gold Cloth. (Saint Seiya!) He arrived on top of the walls of XiaPi right when it was about to fall to Cao Cao.

“Don’t kill me bro; I’m not working for boss Cao!”

“Hey! You’re slashing the wrong person! Boss Lu’s underlings are there! Not me!”

He accidentally saved Lu Bu who was tied up by Song Xian. He accidentally became the son in law of Lu Bu. He accidentally changed the history of the Three Kingdoms period.

When aluminum casted Gold Cloths are worn by generals like Zhang Liao and Gao Shun during the Eastern Han Dynasty, glistering on their bodies… When the soldiers in the camps are sporting mechanical crossbows… When crossbreeding of rice plants appeared on Lu Bu’s territory…

Liu Mang knows that a world belonging to Lu is coming.

- Description from Novelupdates

Just like how everyone adored heroes in their childhood, a certain young man adored those powers hidden in shadows. After hiding his strength and living the mediocre life of a mob character by day while undergoing frenzied training by night, he finally reincarnates into a different world and gains ultimate power. The young man who is only playing at being a power in the shadows, his misunderstanding subordinates, and a giant organization in the shadows that gets trampled…. This is the story of a young boy who had adored powers in shadows possibly eventually reigning over the world of shadows in another world.