I agree with everything you've said and would like to add more.
The MC is your typical romcom MC - a wuss with no backbone who stammers at the sight of any good-looking woman (even his damn cousin, as well).
The part that aggravated me the most about MC is where the FMC genuinely attempts to fix herself. The FMC knows she is an absolute mess and mentions that throughout the entire series. Yet, the one time she gives her all to fix herself, the MC swoops in with his severely misguided "kindness" (it feels disgusting to even refer to it as such) and enables her instead of encouraging her. "Man of strong virtue," my ahh. Withdrawal symptoms are a normal part of getting rid of any addiction. There is a reason why addiction support is a thing. At best, the MC is ignorant and did not know that. At worst, he does and is morally abhorrent enough to enable her anyway. After this point, both MCs make half-baked attempts to moderate her consumption, as if there's any point after her one heartfelt attempt was ruined.
Now, for the ending. I understood the author had health issues, so I can excuse the lack of progressive character development and rushed ending. But is it too much to ask for a single page where FMC says yes to MC's confession? We know she likes him because she blushes a little when thinking about him. But that is about all we get. There is no explicit admission on her end, even to herself.
On top of that, the only explicit confirmation we get of their dating is "I escaped the single life thanks to you" after a time skip to the MC's 20th birthday. I said prior that I can excuse the lack of progressive character development, but I cannot excuse the lack of overall character development. A time skip is a golden opportunity to show such a change, but the author wasted it. FMC is still an alcoholic, and MC is forcing himself to drink beer even though he hates the taste. Why? So that he can be on the same wavelength as her.
I cannot, in good conscience, give this manga more than a 5/10, and even that is probably too lenient.
come-on you're too harsh, being a alcoholic isn't an issue, it's a character trait.
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isn't it cute how look really proper and then empty the entire content of her stomach because she couldn't stop herself from drinking?
jokes asides, yeah this is morally disgusting when you think two minutes longer than "ahah this is a funny cute trait".
this is the kind of writing that """works""" only because there's never any consequences or outcomes to their bad choices,
and if there are any, it's played for laugh and it's light, maybe she get a bit of hangover and say "never again",
then the next page is her downing a comically large mug of beer.
what ends-up happenning is also your perspective on the MC either end-up turning into "poor guy", or "what a scumbag".
he's in the worst spot between being a genuine dude caught between a rock and a hard-place, and a complete ignorant morron.
and ironically this perspective you can kinda see with everyone else in this god-forsaken manga.
-depending on your perspective the FMC is either a naive idiot who dosn't take seriouslly enough her issues,
or she's a complete fuck-up who's a massive burden on one of her coworker.
-her relative is either a sweet lady who knows she has a issue but is severly underestimating it,
or she's a complete bitch willing to blackmail a young man instead of getting actual help.
and i'm not even gonna touch the "romantic aspect" of it, because i think dating someone like that is immoral to start with.
unless it's someone you were already dating PRIOR to their self-damaging behaviours, dating someone who's clearly in need of help seem disgusting to me.
anyway.
this shit dosn't deserve a 5/10, it deserve a 2/10 max.
the writing is shit and end-up sharing a really poorly thought, immoral message.
depending on your perspective, the characters are either completely ignorants and irresponsables at best, or complete assholes at worst.
and beyond that, it's just yet another office-romance about relationship where one guy discover the gimmick hobby of a hot-coworker.
the most you can say about this manga is, at least the art is cute, period.