MTL - Global Game: Comes with Portable Store - Chapter 17 mystery shop

When our protagonist becomes the game character Jun Karentia, she thinks she has it made. She may be just a lowly support mage, but with her knowledge of the game, she knows she can finagle her way to the good ending following around the main character, Fabian. The problem? This game doesn’t end after one playthrough. Jun is prepared to guide Fabian through the second playthrough to the true ending when… Fabian abandons her. Now the Grand Duke Mayer Knox—captain of the Dark Knights and the secret final boss—is determined to have her join his party. Can Jun turn the final boss into the main character? Why is Mayer Knox so intent on having her in his party? And when will these rumors about being his lover stop?!

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

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.