It's quite good drama and not so typical story, as other reviews say it.
It isn't great drama, but it's really realistic story, relationship and dialogues. I haven't seen many Jdramas, but at list this story isn't usual for Kdramas and Cdramas. So if you are tired of same clieche fairy tale-ish love stories and want some real romance, plus forbidden love and taboo subject (Infidelity) you should try it.
Although choices (romance with married man, staying in and choosing toxic relationship) that FL does isn't right for objective viewer but it is soo realistic when you are deeply in love and in this drama that love is believable. I didn't like ML but I understood FL, because we all love who we love and actress played woman deeply in love very well.
As I said her choice to stay in this very toxic relationship when she cried all the time was so wrong, but understandable - it's real life...
ML has nothing to like him, maybe only pity... life is hard to him but he isn't brave strong person himself too...
But drama has amazing SML - he is supportive understanding good and all the things we have seen in many dramas with that kind of SML but he also is different, very very light, funny, positive, playful in good way, someone who can always make people around him (as he does with FL) good mood and smile.
So she has 2 options/relationships: forbidden love with toxic painful relationship, which she should hide all the time, when she needs it the man she loves almost never with her, she can't text, call him free and she can't even complain about it.
and there is second guy, super positive, funny and same time successful in his career, he is always there, always makes her smile and forget bad things, but she doesn't love him, and that is realistic, that can easily happen in real life... and this drama has that (often unusual for melodramas) vibe of realism ...