As a child, the MC was kidnapped with many other children by people from "the demonic path". Since their leader had just lost against the sword saint of the "orthodox path", they decided to brainwash children and infiltrate them into every single key places in the orthodox world to carry their revenge once they're older. So each member of the demonic path takes a few children as their disciples and then scatters. The MC's master is a doctor and someone who tries to leave the "demonic path" with him while making it look like they're accomplishing their mission: killing Murong Xue, the daughter of the sword saint. The girl has a terminal illness which will kill her by the time she reaches adulthood, and they become her doctors. Over time, she falls for the MC and, by the time she's about to die, she asks him to take her v!rg!nity. Since he will die either way (killed by the demonic path if he lets her die a natural death or killed by the sword saint if he sleeps with her), he chooses to comply. And, one way or the other, when the morning comes, she's healed... Now, the world will start coming after the genius beautiful daughter of the sword saint (until now she was left alone since she was sure to die soon) and the "son-in-law" (MC)...

The more time passes, the more amazing both the MC and FMC become (even though they basically only stay at home, making love and destroying the people coming after them), to the point they feel too OP to be disturbed by anything or anyone, which makes things seem a bit boring and keeps lowering my expectations (at first the MC seemed so helpless in this situation, but now...). With no sense of tension at all, the author keeps showing them planning to (very easily) make allies in order to protect themselves (but you don't really feel the danger to begin with... not that it doesn't exist, supposedly). Basically: they identify a useful ally, of course that person has something they deeply wish for but can't have (hair, children, etc.) and, obviously, the doctor or someone else knows about it, then the person comes to the doctor, he gives them his miracle pill, they get what they want and become their ally, then they start planning for the next recruitment...

And while the background plot (things happening in the world while they are passively waiting at home) becomes more complex as they recruit their allies (but you end up forgetting about it since everything is mentioned just once in-between recruiting, anyway), it doesn't feel like things are moving forward at all...

The pace is completely wrong and makes things quite boring. It's a total mess, and characters that have been introduced as important to the story early on (mainly women entangled with the MC) have an appearance rate close to 0 (they are not even mentioned anymore after a while), and I can't remember most of them... Even small things like the MC trying to convince the FMC to have children with him, are mentioned once and forgotten (even though he acted like it was his new goal in life)...

It feels like the author is just going with the flow, rather than actually telling the story she/he had in mind at first.