Express of love comes in many form it doesn’t need to be in words. The relationship wasn’t randomly formed though? It was very well hinted from the early chapter, from the moment they got intimate the relationship/feelings were forming already.
Mc isn’t a strong personality type since he grew up blindly following orders and was very afraid people would leave him again. He is already cool being an excellent hacker but it won’t change his personality overnight yk.

ok did anyone else get pissed off by how their relationship just randomly formed and nothing was said abt it like one day they’re just having sex and the next they’re lovers? Also the fact that they never said I love you to each other (unless i missed it cause i lowkey skipped a lot). Seriously tho I don’t think they ever said I love you to each other. To top it off the mc is so bland like he genuinely does not have a personality. They could’ve done so much with him being a hacker and smart as hell but no he was just a boring guy till the end.