Iron Blooded - One: Front Lines

A man is reborn into the world of Avatar: The Last Air Bender as a waterbender from Katara's tribe. Best of all, he was the same age as her, and he had a system with him to help.He knows the future and a system that lets him continuously get stronger by completing quests or long-term missions, as well as giving him the ability to copy abilities from others for himself. He will become invincible in the world of Avatar, even more so than the Avatar himself.

He is high above, the mysterious and terrible King of the Wild. With one glance, he can see people’s romances. He hates women to the extreme, but at his first glance of her, he dotes on her and spoils her.
She is a humble transmigrator, a miracle doctor who doesn’t care for the many handsome men around her. She only wants to become strong, to be worthy of that god-like man. But when she’s finally sure of her feelings, she finds out she’s already been married for years…
……
When wronged：
She uses strength to hit the big handsome iceberg-like man in front of her eyes. “People say that I’m not good enough for you, but it is you who is an old cow eating tender grass!”
A man seizes the main point and laughs like an evildoer. “This husband has to eat the grass to confirm if it is tender or not!” He puts out the red candle……
……
The world says：
The barbarian king has no heart and has no passion.
A pregnant woman very miserably thinks,” If he has no passion, then who is responsible for this big belly?”

- Description from Novelupdates

Bought it right away.

On a certain day, Xu Xing suddenly received yin-yuan eyes; he could see a red string between lovers. Then he discovered that he had a tight connection to his own left hand.

Xu Xing: I TM …… will I be ‘solo’ for life? : )

The second day.

Xu Xing suspected that he had seen a pair of ‘gay’s. The left side of the boy’s body had two red strings. The one in front was tied to his hand, the one in the back was tied to the boy’s right side.

The bottom of Xu Xing’s body suddenly tightened. Trembling in fear, he turned his head — only to see his ‘local area’ connected to a red string tied into a beautiful, intimate bow that was attached to the school grass sitting behind him ~

Xu Xing: Excuse me???

- Description from Novelupdates