Starting the Game with Godlike Vision - Chapter 8 - An Uneasy Alliance

At 18, Alex Kain is whisked away to Eryndor, a game-like realm where he gains 'Skill Synthesis', a talent to fuse skills into godlike powers. Battling monsters and conquering dungeons, he builds a harem of strong women drawn to his might and charm. With the power to return to Earth bearing incredible resources, Alex faces a growing threat that endangers both worlds in this epic of adventure, romance, and ambition.

She is the slow-witted idiot of the Prime Minister’s Residence. Everyone bullies her. He is the most respected and unfeeling Prince, with frightening ability and absolute envy! Together, they are conferred an imperial edict of marriage.

She acts stupid and tries to decline in every way possible while he despotically escorts her into the wedding…… everyone ridicules the match, but no one knows that the “idiot” has transformed from a loser into a talent.

After the marriage, when they encounter the Empress Dowager examining the room, they act in concert with each other and pretend to be two mandarin ducks deeply in love. Afterwards, she laughs, “The performance has ended. Your highness, please return.”

He laughs softly, “Since you’ve got onto this Prince’s bed, don’t even think of getting off.”

- Description from Novelupdates

In the Abyss, all beings are imprisoned, struggling bitterly to survive. One day, in the eternally dark lower world, a young boy has a chance encounter and catches a glimpse of the upper worlds. He is fortunate to witness wonders beyond even the most beautiful dreams. Realizing there are worlds beyond his own, he refuses to settle for mediocrity and vows to ascend to the top step by step.

There was a Senior Brother and a Junior Sister. One of them was transmigrated to this world and had cheats while the other was the reincarnation of a Great Emperor.