So this most recent chapter (44) has highlighted what I think is probably the biggest problem with the 'main' ship, that we don't get to see most of the Random Chatting. In the beginning we got to see some of it like the music but there's been a running theme of 'implying' that they're having casual chatting and getting along without showing it, and that's honestly a major problem. Sure I can get why she'd care about the stranger on her phone when he helps her out in a pinch but he's not the only one who's helped her out, let's see them just causally getting along without the MC using it as an opportunity to 'happen' to run into her at the vending machine or something. Show us the chemistry these two have over the app, as that would give us an opportunity to understand what's her face similar to how we understand Hamin and Yuri as well as establishing that while the 'other girls' might be fun and have some interest in him they don't have the same sort of connection as main girl has. I get the random chatting was a hook to start off the plot but it really should be show-cased more, that way I can get behind the ship of how these two want to get together easier, until then all this drama about the MC being a creep and chasing after main girl when I'd be fine if he went after either of the other girls (Yuri's got enough history and chemistry that I'd be fine with her moving in instead of Hamin) just feels frustrating and leaves me thinking that this is actually supposed to be a martial arts comic.
Also while I've got to agree with some commenters that MC being at the beach shouldn't have really given off stalker vibes (in of itself) given that she intended to invite him, SHE found HIM, and he was with his own friend in an area that was just nearby where they were (also keep in mind that as established at school, going to the beach seemed like a fun idea to many), but then you remember how the dodgeball game went, the vending machine scene, and how he did end up in the same club as her despite probably not showing a ton of interest or skill at debating in the club, I can get why she might take something that may have otherwise come off as coincidence as a sign of stalking. MC hasn't exactly been covering up the obvious tracks that he likes her, so I'll give her some leeway in thinking something that could easily be innocent as being more because MC has a pattern of behavior to support her theory, even without considering all the things he's done that she doesn't know about.