My Dead Mistress Returned as My Wife's Bestie

Summary

My mistress tries to take Scarlett Astin's place as my wife, so I kill her, burn her body to ashes, and bury her in the middle of nowhere.

Five years later, I become a general manager. Scarlett gives birth to twins, a boy and a girl, and we settle into a happy life together.

I gradually forget about the past.

Then, after Scarlett is discharged from the hospital, she suddenly says, "Don't forget to invite Madeline Brown to the twins' sip and see. She's an old friend of yours, right? She took such good care of me during my hospital stay."