
oh noooooo

Please no

it's been a while since i've read it, so i can't remember specific chapters or events, but i've only read up to chapter 60. here's a nice teaser picture though: https://imgur.com/a/csxLc

WTF?!
That looks a bit like he either caught his bf cheating on him and is distraught and filled with rage... Or he just realized that Minoh is in love with him and he is completely weirded out because he doesn't know how to feel about it. Or he just realized that HE is in love with Minoh and he is completely weirded out because he doesn't know how to feel about it or if he has a chance with Minoh.

SPOILER
.
.
.
.
.
.
.
.
.
In that panel Junoh is thinking, "Crazy bastard," because his mom just told him that purple-haired guy (hereafter PHG), whom she thought of as Junoh's friend, came over to his house. PHG used to bully Junoh (although before that they were friends), so Junoh is angry/terrified about PHG pretending be his friend again in front of his mom. He thinks PHG is coming after him again. PHG's name is Jaehee or something. But Junoh is no longer some wilting flower.

Ah.
Yeah, latest chapter showed the ugliness of PHG so him coming round would definitely illicit that reaction.
But what does PHG have to do with the tone of the series of Minoh and Junoh's love story? How does he interfere with things if M and J both hate PHG and see him for the ugly borish idiot he is?

I reread (well, as best I could considering how limited my Korean is) the raws and it looks like Junoh and Jaehee (that's PHG) have a pretty complicated past that I think needed to be addressed before the story could really get anywhere between the MCs. Because of Jaehee's appearance we get to see a side of Junoh that we hadn't seen before (he's not as fragile or innocent as he seems), and we also find out for sure that he's gay.
By the way, while the story does take a dark turn for a while, it ends with almost the same sort of lighthearted mood that it started with (except now we have a much deeper understanding of some of the characters). So don't worry, because the fluff doesn't get permanently derailed.

No. It's raw spoilers for http://www.mangago.zone/read-manga/how_much_i_like_you/
Which is Lezhin. There is a STRONG pattern of love stories on Lezhin turning dark. Especially, the queer ones but I've noticed that it is mostly for yaoi. There are VERY FEW happy gay sweet love English translated series on Lezhin. There is always ANGST, dark past, being physically attacked, etc.
Some go a bit angsty like My Girlfriend's Ex-Boyfriend ( http://www.mangago.zone/read-manga/my_girlfriend_s_ex_boyfriend/), but it never went to the levels that I see in regards to yaoi or male gay/bisexual characters.
I'm STILL pissed about Innocent Sin going so fucking dark.
Foxtoon is pretty bad at that as well: http://www.mangago.zone/read-manga/raising_a_bat/

This is perhaps a Korean tendency rather than a Lezhin tendency. Westerners (esp Americans) often expect a happy ending. Koreans do not. Plus, Korea's really homophobic for a developed nation, so regardless of whether the authors themselves are homophobic, stories centered around gay characters do often take a dark turn. (I'm actually in Korea right now and people get pretty uncomfortable if I bring up homosexuality.) But it's not just LGBTQ themed stories. A lot of (extremely heteronormative) Korean dramas do this as well, especially Hong Sisters dramas.
spoilers?
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
damn if you thought school life would only continue to be fluffy and cute, you're in for one hell of a surprise and a bitter serving of angst