
the story is interesting, I could give it a thumbs up. It's just that we are getting nowhere with all these clues, and mystery about Gaeul's death. I'm inbetween the thought that he was murdered, or he really committed suicide. But here's what I think.
So we all know that Gaeul and Hayoon have some intimate relationship between the two of them. And Hayoon is obsessed with Gaeul.
And there was a chapter where hyungsik told Hayeul that Gaeul was just toying with Hayoon. And now, we found out according to Gina that she was referring to someone when that guy told him about Gaeul regarding to suicide that happened before she graduated.
So I feel like that guy who also died who was kept hidden, is somehow related to the death of Gaeun. Maybe, just maybe..the reason why Gaeun decided to go to a boarding school in a middle of nowhere was because he has hidden feelings for Hayeun? (just a guess) and the reason why he wants to transfer because he doesn't like what he's feeling. (another guess) Or maybe he just wants to be free and do what he wants away from all the worry of his parents. (according to seojun)
So going back, when he transferred there, that's where he met Hayoon, and Hayoon became obsessed with him. And then he had sex with Hayoon, that's why he wrote on his diary that 'I slept with Hayoon' 7/28.
And so let's go back to the person who also died on the same year Gaeul committed suicide. Maybe the reason why that person died has something to with the 'Reading club' that's why Hayoon told her (seojun) that she's also an accomplice. Like bullying that person, framing, or pushing that person into a corner which led that person into death, and Gaeul was also part of that person dying. Like remember what that member of the reading club told Hayeul about how he's scared of Gaeul because he's scary, like he has some kind of a switch like a dual personality or something which Hayeul doesn't know of.
Add the fact that the reading club isn't simply just a club. Like they do something mean to other people for the sake of boredom. So the guy who died, killed himself? Or actually died from something. Amd the 'Reading club' cover it up, so no one will find out about it. And then Gaeul on the other hand felt really really guilty about it and he snapped out from what they have been doing up until now, so then as days passed, guilt was killing him slowly. Up to the point he had nightmares of the person who died and was making him feel guilty. Since he has a weak heart, he won't be able to handle such huge guilt. The reason why Gaeul killed himself.
Just a guess? My theory, since the story is heading nowhere, alot of questions still unanswered. Story plot progressed so slow and questions still keeps on coming while being left unanswered. Well atleast these are what I've come up with. Hope it updates

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Galhwa does NOT deserve to have some power wtf, beelzebub corrupted his body, and now he has powers too. Da heck. I just wish that Junho gets much more stronger since his emotions gets in the way. Damn that part where he was about to kill galhwa but stop coz he remembered someone.

so his power is 99% healing and 1% Virus (like disabling powers for a week or so) but what happened to his past tho? there was something like blowing up the whole building and injuring people. How is that possible when his power is healing and ??? which only affects people who also has powers. Does he have another ability far greater than what we know right now? Can't wait for the next update (〜 ̄△ ̄)〜
See comments saying it has some yaoi vibe in it.
Yaoi finatics will always find yaoi even in places where there isn't any. A good friendship between males? Obviously they love each other. Two characters hate each other's guts? They're obviously fucking behind the scenes. A character looks at another character a certain way. He obviously loves him just confess already! Don't worry about it some people just have hardcore imaginations I mean I wouldn't be against some of those fantasies being real.
Yaoi Logic (≧∀≦)
There is (probably) some fan service but there is definitely no canon yaoi action going on.
I've only read the first two doulou dalu series so far so I can only take a guess about the fanservice but the other two were so painfully hetero-normative that this one is definitely going to be the same.
(If you were a man I'd marry you, I wish you were a girl, in our next lives I hope that I'll be born as a male so we can get married, etc.)