My Dragon System - Chapter 4: Becoming a Mage

Riku Barusak is a hard-working child. Despite possessing an innate superior physical strength and having withstood harsh training she fails to unlock her talent as a spiritualist. The failure results in her being thrown away by her family.

Abandoned, the only ones that extended a hand to her were the demons, the greatest enemies of the human race. Serving under them as a soldier she becomes a weapon of human slaughter, a fiend that should never have existed.

500 years ago, Chen Xi was devoured by a crack in the void and was transported into a cultivation world.

500 years later, he returned back to Earth after enduring through several hardships and discovered that only 5 years had gone by.

…

In the courtyard, beauty at the side, a candle flame wavering.

A gush of clear wind, half a full moon, the peach tree remains unchanging.

…

Wait, whose kid is this?! Why is she calling me papa? Gazing at the little girl in front of him with skin as pale as jade, Chen Xi froze.

…

　
Returning home from cultivation, starting as a stay-at-home dad.

In this life, not fighting to be a king nor claiming to be a tyrant, only praying to peacefully be a wife-pampering mad devil and a child-protecting daddy!

- Description from Novelupdates

After assisting the man she loves with all her heart to the throne, Li Wanrou dies miserably in the cold palace, her dead body wrapped in a broken mat and thrown into the disorderly funeral hillock.

My handsome, overpowered dad, who only ever cared about me, ate something strange and turned into the Demon King. He used to be the sweetest, most doting father, but now he’s the final boss?! Because of this, my dad is fated to be killed by the male lead, and I’m destined to die lonely while mourning him. At that moment, I returned to the past and realized that this world is actually a game! I couldn’t prevent my dad’s descent into darkness, but no matter what, I must turn him back into his original self. If I succeed, I can get my loving dad back, right? For now, I need to get close to the male lead, who’s destined to kill my father…! So, I became a Holy Knight and even managed to be adopted as the ward of the Pluto Ducal House—the male lead’s family. …The problem is, I’ve become way too strong. As long as I get along with the male lead, my dad might avoid being labeled as the Demon King. “But that’s strange.” “…What is?” “Your lips… they’re heart-shaped.” “W-what? Don’t look at my lips!” At that, the male lead tried to avoid my hand and ended up rolling under the bed. “Ahhh!” “…?” He’s supposed to be the strongest person who’ll one day kill my dad, but for now, the male lead is just too cute.