He wasn't looking for a heir. He didn't plan to pass on his legacy any time soon, and wasn't eager to care for a child-- let alone that of a concubines.

Concubines were selected for looks, cosmetics--not their resilience, strength, nothing of this sort.

He couldn't even anticipate good genetics.

"I hope you know I'm not going to be caring for the bastard,"

Sukuna grunted, eying you critically. This was your responsibility now. And he hoped for something more than a weakling.