2 things to consider here. (Disclaimer take this with a grain of salt I didnt read the novel just repeating what some older comments said. You can probably find them if you comb through)
1) he gets with her after a timeskip, and they are both adults
2) he was an adult originally before transmitting into the novel. Thats also why he feels no romantic interest in any of the students, he feels weird about it.
Yes there is a moral debate on this (im personally pro no romance) but what can you do
Welp, she’s better than Hayoon imo, and it seems like a super slow burn so I’m cool with this.
Especially since he’s set up to join her organization, but I thought he was also planning on betraying them after using them for his plans with the plot? I forgot if they’re good, bad or grey (it was mentioned that they took jobs to kill if it was a morally necessary evil or something like that?)
Also I love Rachel too, but she’s a princess with responsibilities so it wouldn’t work out TTvTT but on the other hand if she already has an heir… OwO

I fucking hate this hayoon girl,like hello obsess so much? She's acting like hajin belong to her like girl fuck off,I might drop this is that freaking girl continue as she is, compare to Rachel that admiring hajin from afar nayoon is so fucking obvious and jealous I don't like it,I've read so many Romance sht before but I can't seem to tolerate this type of obsession.It will be good if hajin don't end up with anyone else and be with the child.he was raising. Fucking nayoon she's ruining the story with that bullshit