It's true that the ML noticed that the MC was too out of character with her transmigrated body and sought to manipulate her when he found out that the MC was a transmigrator.
He needed to manipulate others in order to survive because he was still very weak at first, but in spite of that, he always listens to what the MC has to say, and after a while, (when he fell in love hehe) he wanted to treasure the MC.
So I wouldn't say that she was manipulated, the ML just taught her how to live in their world, and the ML also doesn't force the MC when she thinks she can't do what he says (like mass murder, that's the MC's bottom line, or when it disturbs her three world views).
The story is not based on a single world, since later in the story, the MC and ML will travel to different worlds together. (Because the MC becomes homesick and wants to go back to her original world, the ML decides to take her with him to many different realms, so that he can coax the MC. The ML just loves her THAT much.... But that's not really the only reason 😛) Thumbs up to the author for having such an imaginative mind. 👍👍
When they move to another world, though the ML might have the same body sometimes (I'll just say that its because he becomes someone who's VERY powerful that he can easily overcome the limits of the other world/s), the MC will become drastically different (Because in the end, she doesn't have any kind of powers at all), there was even a time when she became a fish and couldn't remember the ML! Hahaha! 😂
Mutual feelings starts at around chapter 283, and fyi it's very satisfying. (〃￣ω￣〃) ゞ
An age gap, (the hubby is older 😘) which is not really that uncommon in the ancient times.
The ML was a renowned assassin, and the FL was an abandoned girl that they picked up (I'm just glad that she didn't meet any dangerous people 😅) while they were eating at a restaurant.
It's so cute seeing the ML battle against his own feelings for the FL, it was amusing to see him try to differentiate if his feelings towards her were of a romantic kind of love or a parental kind of love.
But in the end, because the ML 'cooked' the FL's rice, he HAD to marry her anyway, hahaha 😂