Their friendship ended by them insisting on Kwon shi-hyun to continue leading Tae Hee on to break her heart. He realised his friends would not be understanding and decided to keep it a secret from them which ultimately lead them to hate and distrust each other. Overall, I think it was because of his friends being stuck in their ways and not realising that Kwon Shi-hyun actually fell in love with Tae Hee

Especially Choi Soo-ji!! She wanted to be right SO BAD about Shi-Hyun not actually liking Tae Hee

Hated Lee Soo-ju when he told Tae Hee about the game, hated him so much. 

Did you feel like the ending was rushed? I was really disappointed with the ending as I wanted to see more screen time of Tae Hee and Shi-Hyun reuniting and reconnecting but it just cut there 

Wish they released more episodes or tried to not rush the ending but oh well

I went with the cliche ending that everyone is now matured having to go through such tragedy. Shi-Hyun and Tae Hee are now together, trying to work out the next steps of their lives now that they’ve matured and the situation no longer hurts them

what ending did you come up with?

so many blame Joy for breaking their friendship. She was a stranger who happened to get tied up in the mess. In fact, it was them who dragged her in. Su-ji came up with the idea, first of all. And also, Joy came into their life to change Si-Hyeon. And his priority had to change. Of course they could've maintain their relationship well, but are they really friends if they cannot respect that. In my honest opinion, Su-ji broke it, mid-episodes, out of jealousy, and that was it. 

 Piya_fangirl_of_yibo:

so many blame Joy for breaking their friendship. She was a stranger who happened to get tied up in the mess. In fact, it was them who dragged her in. Su-ji came up with the idea, first of all. And also, Joy came into their life to change Si-Hyeon. And his priority had to change. Of course they could've maintain their relationship well, but are they really friends if they cannot respect that. In my honest opinion, Su-ji broke it, mid-episodes, out of jealousy, and that was it. 

Those people that said Joy reined need to put a sock in their mouth