MTL - Start with a Mechanical Hunter - Chapter 120 antispecies cell

Su Wan is a Realm Destroyer. She shuttles to different time-spaces using the identity of the “Cannon Fodder Ex-Girlfriend”, dedicated to plotting how to happily tear apart the male protagonist and the female protagonist. –There’s no such thing as protagonists who can’t be torn apart, only Ex-Girlfriends who don’t work hard enough~

The two faced number one female spy transmigrates to a different world and becomes an outrageous idiot girl. When she woke up, what she had to face was consecutive blows of the decline of her family clan, her crippled martial skills, and her disfiguration. To protect her family, she must obtain the treasured book, obtain outstanding achievements, summon a dark beast army. Wait and see how in this unfamiliar, dark magical continent, she dies and becomes a demon then steps up to the top, making all of the formidable people in the world bow down to her in respect.

- Description from Novelupdates

Xiao Jinghuai's home has a little thing, soft and adorable, lively and mischievous.Rather than calling her a wife, it would be better to say it's like having another daughter.Some people say: “Young Master Xiao pampers his wife to the point where she only needs to open her mouth to be fed, she's almost become useless!”“Whoever says that, throw them into the sea to feed the sharks!”Another person says: “Young Master Xiao's wife really doesn’t look that great, nowhere near as beautiful as so-and-so!”“Whoever says that, gouge out their eyes to feed the dogs!”Yet another says: “Young Master Xiao spoils his wife excessively, he has become a tyrant of his generation!”“Who says so?”Turning around, just to see the girl's bright and charming little face, “I said it! So what do you want?”He pulled her into his arms, didn't want anything, just wanted her to be his little princess...(Even in this world full of charms, I only have eyes for you.)

Crossing to One Piece world, he became Roger’s younger brother.