First off, I just wanna point out that the poster is misleading. There are three characters who aren't on it and at least 2 of them should be. If they added these two/three actors/actresses with everyone looking in the right place or at the right person, you would have a basic understanding of the storyline as it first starts. Apparently, this series is about someone who likes someone who doesn't like them back.

I usually like to write a detailed synopsis about what this show so major spoilers ahead:

The storyline takes place in college. There are two main couples.

The first "couple", the main leads, are best friends, with a one-sided-love-triangle-trope. The guy likes the girl, who is his bestie, but the girl likes someone else who likes her back.

The second couple is the "Magnet Couple" or "Campus Couple". The girl in this relationship has a female "friend" that has a kind of stalker-ish one-sided love for her obviously taken boyfriend.

In total there are 9 characters, 4 guys and 5 girls. 3 of the guys including the ML and SML are roommates and 3 of the girls, FL and SFL, are roommates in the separated dorms. There are "what do the women think" and "what do the guys think" opinions of the same issues and problems.

Then there's the mysterious author of a post that starts off with "Dear M". This is a post confessing that some mysterious person likes someone in their Photography and Appreciation class. All of the above characters share this class so everyone is wondering who wrote this letter that was posted on one of the school's forums for everyone to read. Everyone is trying to guess who wrote the letter and who is "M". More letters follow after.

There are a few things that annoy me about this:
-The campus couple and their lack of communication. It's not that they don't talk, it's just that they don't share important need-to-know crap. There were a lot of red flags with the stalker friend, but SFL just pushes her suspicions aside and by the time she finally confronts the stalker friend, it's a bit too late.
-Also, the SFL falls into the "I'm going to do and say this to my boyfriend but I'm secretly hoping that my boyfriend won't listen or do what I say" scenario. Then she runs crying and whining to her friends when he actually just does what she says because dude is just a nice guy.
-The boyfriend, the second male lead, is played by Bae Hyeon Seong. While he's nice to look at because of course, he looks like BoGummy, most of the time he looks lost and sad. If it isn't his girlfriend, it's his studies. Every time I watch him, I think, "Poor guy... doesn't even know why he likes his girlfriend." Lol. He's still a good actor though just his character seems depressing every time he's not smiling.
-The FL, played by Park Hye Soo, looks like she belongs in high school or maybe even middle school. I'll be honest and say that I don't think she's a suitable FL. The way she acts all shy and naive is definitely out of place for a uni student. I get it she's experiencing first love vibes and all but it's the same kind of acting that keeps going on with her. Also, her kiss with her crush is while drunk and she barely remembers it the next day. Really?! That's the worst kind of 'first kiss' cliché.
-Another thing I really dislike is the FL lying and saying she likes this and that so it's the same likes as the guy she has a crush on. She managed to get inside information about him and used it to her advantage. So she pretends she's interested in everything he likes. Literally. WTF. Because of this, the career path she starts thinking of is the one that her crush says she would be good at. Go figure.
-The same goes with the stalker friend but her route about finding out more about her friend's boyfriend was more in a stalker-type way.
-There's a scam that's very obvious.

What I like:
-So far I love the acting of ML, Jaehyun and I really think that he's suited for this role.
-I love the bestie relationship and their story but more so with the ML and how he really knows his best friend and the way he takes care of her more than she does of him. She does like one major thing for him but that's really all I can r member. He does all these little trivial things for her and it's endearing even though she's oblivious.
-the Karaoke scene was very well done and I loved the beginning where it seems almost like they can't sing but then the duet comes and it's perfect. They pulled off the duet in a creative and interesting way. It's my fave scene so far that I rewatched that scene a few times already. I'm hoping Kdramas do more scenes like this. I hate it when they have an actor/actress who can sing but in a drama, they "fake" sing terribly.
-The storylines are interesting enough and so are the backstories of some characters
-The road trip scene with the lip balm was hilarious and the curse cafe was funny too.

All in all, this is holding my interest but when I really think of it, all the women are written poorly with more flaws than the guys. The women are either clueless, naive, b*tchy, stalker-y, or victims. Sigh. Right now I'm at Ep6 and I like the fact that they're dropping a lot of episodes at once. I can't rate too high as of yet but I'll update my review later if necessary.

Update:
I was glad that this series dropped 6 episodes in 2 parts at once because I don't know if I would've been excited each week to wait for new episodes. For me, it's started getting draggy. I fast-forwarded a few parts because it wasn't holding my interest.

I'll say that ML, Cha Min Ho played by Jaehyun, was probably the only character I was rooting for because I got irritated with everyone else. Everything ties up at the end and once that happened it wasn't like fireworks or cute "awwww" feelings. It was just so so. All of a sudden, the couples were just... boring. There is the standard, typical k-drama trope where the actresses always look surprised every time they're being kissed. (What's up with that btw? The guy goes in for a kiss and the girl is always surprised. Even the ones in relationships. It's always like watching a bunch of teenagers kissing for the first time.) There was a wedding dance that was so cheesy that it should've been cut out and as for the villain girl and guys, nothing much happened to them. The mystery of Dear. M was answered and left much to be desired. Everyone looks bored by the ending scene and it made me bored. Overall, it wasn't too bad but not great either. Jaehyun's acting was really great and gawd knows he's got that eye batting and longing looks down! I'll probably rewatch his singing and cute confession scenes.