Notes From Reviewer

Title 

For a story that is very well written, I'd say the title kind of brings it down. It's too long for my liking, something shorter would be better. Maybe just a shortened version of what you have now. I don't know, I'm not telling you to change what you have (because usually when it's posted there's no point in change) but the title is definitely too long. The title does have meaning to it within the story, which is good, but eh. I don't really think it's a title that would blow someone off a roof but there's nothing that can be done about it. 

Description & Foreword 

After reading, I realize the description was taken from inside of the story which is considered clever in my book. The description can imply obvious cheating which is a given pretty much but it didn't really captivate me in a way that made me want to read it, which is okay too because everyone has different tastes, but it was a good read after getting through the chapters so I guess never judge a story by it's cover (or a fanfic by it's description). 

Plot

I decided to read this fully first before jotting anything down but I really like how you put a real world aspect into it. From watching English teachers/Ex-English teachers in Korea, I learned that the trains do close at a certain time so when Hyeusng offered to call him a cab because the trains were closed - I just really liked that so I pointed it out just now. 

As for the plot itself, I wish it was longer. Like, after the scene with Chanyeol and Kyungsoo and Kyungsoo knowing that Chanyeol tasted like someone else, I wish we could get more backstory on that but it is what it is. The fanfic is pretty good at messing with a Baekyeol/Chanbaek shipper for sure, it makes you think that they might get together but kind of crushes those hopes at the end. The idea can be seen as a little cliche because of the cheating, the 4 group friendship feeling crap going on between Jongin with Kyungsoo and Baekhyun with Chanyeol, if that makes some kind of sense, but you took the idea and made it your own so that's always good too. It makes up for the cliche-esque kind of idea.

Writing Style 

For writing style, I'd say it's very good. Your dialogues felt pretty real in a sense, like this story happened to real people, not the idols, but like real every day people. Your paragraphs went together nicely, too, which made it a very enjoyable story to read overall. As for grammar, I feel like I may have saw a typo-grammar mistake, like a very small one, somewhere in the first chapter but I'm not sure - that may have been my eyes considering it's pretty much 2AM now. 

Characterization 

Baekhyun - He's having the same war in his head as Chanyeol. He knows what he is doing and what he wants is wrong because Kyungsoo is his friend but sometimes our basic needs are greater than common sense. He wants Chanyeol but doesn't want to hurt Kyungsoo which is pretty considerate of him but since his want/need/craving for Chanyeol seems greater than his common sense (and the moment Chanyeol touched him he knew that's what he really wanted).

Chanyeol - You can tell Chanyeol is having a mini battle with himself after he makes the rash decision to sleep with Baekhyun the first time. During the act when Kyungsoo almost catches them, it's pretty obvious he doesn't care about what he is doing until after the deed is done. It seems like the guilt kinda kicks into overdrive and he leaves Baek by himself. Though I like how when Baekhynn comes home from that party at almost twelve in the morning, when he's waiting for him, he just goes and does it again, realizing that he kind of wants Baekhyun but doesn't want to break up with Kyungsoo, it seems. 

Jongin - We don't know much about him but he seems like the friend most people would want. He's pretty supportive of Baekhyun and even covers for him which is sweet.

Kyungsoo - I feel like we don't know much about him either. We know he is currently with Chanyeol and feels happy with the taller man but I feel like he can semi-sense something is going on when he catches Baekhyun with Chanyeol's shirt but honestly, we will never know. I feel like he definitely knows something is going on because of the ending part too where it says that Chanyeol tastes like someone else but we will never know what he will do.

Flow 

The flow was very good as well. Like I said in the writing style section, the paragraphs went together nicely. The dialogue was good with a real feel to it and nothing in the story felt absolutely rushed. It felt like you took the time to actually think out what was going to happen. 

Personal Enjoyment 

Whoops, almost forgot this section - what a derp I am. Anyways, I think thos was very well written overall and I did enjoy it. The concept of cheating always interested me because I always wonder what motivates people to do the act instead of leaving their partners. I'll never understand it but it's always been a concept I've wanted to write in a fanfic (who knows - maybe I iwll one day) but you executed the idea nicely so that made it quite enjoyable.
GOD, I hope I didn't leave anything out.