I can understand where Gyeol is coming from, imagine the love of your love, someone who got you out of suicidal times ends up dying suddenly.
You're lost and in intense grief, he has insomnia and is likely prone to depression too (that's just an assumption tho).
You get asked by a ton of people about your loved one mere days after it happened and they just want to gossip and entertain themselves with the news.
Suddenly a guy shows up and asks the same, even pretends to know them while you aren't aware of any connection to them, of course you'd be pissed and think he's the same.
Then he even camps outside their house and knows all these tiny details, how would you feel?
I think there's a mixture of grief, jealousy (of not knowing something about his beloved) and irritation at play.
Too many coincidences so is he stalker?
Those are likely assumptions and based on how they got to know each other, I wouldn't be all too kind afterwards either.
He gets nicer later on but still defensive, he keeps people at bay because he has his own trauma on top of his grief.
And yeah if I heard someone was gay and I don't know the person well enough, I'd be a bit uncomfortable at such a request too. Different topic if I'm friends with someone and trust them.
Based on that, I don't think his behavior is unreasonable + I think most people in RL relationships are kinder and more attentive to people they love so it's natural to treat people differently based on how much you like them.
I don't hate them and still treat them either kindness but for close friends or a partner, I'd jump through hoops to help them.
i won't say i don't like the story, but like,,,,i can't seem to forget how hangyeol treated redhead doyoon before he realised that he's our mc ,,,,,i don't know why but those assumptions are really,,,,,weird, like just because he heard a rumor he was like if i go to his house he'll try smth with me, accusing him of being a stalker, and i know these instances are made fun of later, but like i just can't forget those,,,,readhead doyoon really does not deserve any of this (even though it's not him in his body, but im just saying) hhhhh anyway that maybe just me