I just finished MTLing this story, so if you have any questions ask away!
It was emotional because the leads "broke up" after their 1-year contract expired. The MC was sad & mopey for a little while, and we read about him moving out and starting anew. Both leads have never been in love before, and the ML wasn't aware that he loved the MC at that time so they parted ways. The angst only lasted for like 5-10 chapters though, before they got back together as an actual couple this time!
I get what you mean about it being a little slow, I wasn't really blown away until I got 40+ chapters into the story, and now I view this as one of my favs!