My Black-Bellied Boyfriend - Chapter 6

In the tenth year after the new era, the world finally came to an end. Zhang Mu truefully waited for his death, but unexpectedly found that he had returned to ten years ago. With his memory about the future, he swore that he would change the calamitous history, saving the earth from being destroyed! Walking dead, zergs, evolvers, and various mutated animals… nothing can stop him! The first step is to retrieve his identity as an era merchant , then find all the treasures he can remember to enhance himself!

- Description from Novelupdates

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.

Mistaken by the system, Xiao Jinsheng, who transmigrated into an apocalyptic book world, becomes a malicious supporting female character who has competed with the protagonist since childhood.As compensation, the system promises to assign Xiao Jinsheng five handsome and mighty bodyguards.A mysterious and stunning snake-man with long violet hair, a proud and sharp-tongued cat-eared youth, a charismatic black panther youth brimming with raw energy, a gentle and thoughtful sheep-man 'mommy,' and an elegant, noble Dragon Sparrow Beast Husband ready to fly her to victory.With just one glance, Xiao Jinsheng recognizes these men as her long-lost husbands.The system tempts her: punch the first button and get five gorgeous husbands, letting you revel in a life of love and luxury.“11111!” Xiao Jinsheng frantically presses her fingers onto her 'husband’s' abs on the poster.But who would have guessed that even systems lie these days?Where are the promised gorgeous and devoted husbands? What she receives instead are five executioners!The enigmatic snake husband suffers abuse and is sold off to the black market; after escaping, he only lives to kill her.The cat-eared youth files for divorce daily, the dashing black panther youth terrifies her with bloody threats, the noble Dragon Sparrow avoids her like the plague, and even the seemingly gentle sheep-man 'mommy' turns out to be a wolf in sheep’s clothing.Xiao Jinsheng treads on thin ice, relying on the world’s mechanism where a Beast Husband must follow his wife in death to ensure these murderous husbands can’t harm her.She works hard to strengthen herself. Meanwhile, on the other side of the Mist Continent, a Demon Lord is deeply devoted to her, the King of the Deep Sea Mermaids falls for her at first sight, and even the Silver Dragon of Cloud Island stubbornly camps in front of her door.The five Beast Husbands, who were initially clamoring for divorce, drop to their knees with a slippery slide, now refusing to separate even in death.

This legend tells the tale of the protagonist, Kuroki summoned to protect the demon king from the hero.

Kuroki, unbeknownst to him, suddenly came to another world. He was summoned by the demon king, Modes. The territory which the demon king overrules was in the midst of being destroyed because of the hero. He had no choice but to bow before Kuroki.

“Please save us, Savior Dono!”

Kuroki nodded, deciding to save the demon king due to an unexpected turn of event.