Yes, the ML is nice... but he's rather pushy so far. he and the FL hardly know each other at all and yet he was immediately smitten, and even if he doesn't mean to, he's been pressuring the FL quite a bit. Fl clearly wants to at least take things slowly ("Since I don't even know my own heart, I didn't want to carelessly plant expectations. Or give him false hope.", "I feel like I'll be the one getting hurt.") even if she enjoys the affection and support he's giving her, but he's already dreaming and devoting himself much further than that. ("If I keep clinging to this pathetic, one-sided devotion... Will there come a day... when my aunt and Yeon-woo finally meet?")
While this absolutely has room to grow and change, right now it feels like ML could turn out just like every other ML.
The way FL often thinks also feels like foreshadowing right now, as well as the way this is titled The "Villain's" pure love, yet we've yet to see any villainous behavior.
"Could a voice hiding a secret motive really sound so sweet?" (Chap 26)
"I can feel so well that those words are not obsession and restriction, but care and love."
It just feels like it won't be much time before the other shoe drops.

Umm why're some people hating the ML???? he's such a nice guy