Agree, after all he has done and how things ended that extra seems out of place. The other extra is great tho. Kou is trash but like you said it was well developed actually I would say the story flow was even better than a lot of simple plot but great mangas out there even so the thing is when authors create a hateful character as MC it becomes really hard to enjoy the story thats the problem. MCs cannot be thrash cause if they are it kinda ruins everything their mistakes have to be "forgivable" otherwise its doomed. A similar thing happened to my favorite Shonen AI "Given" Aki was such a jerk to Haru that their ship sank already and there is no saving it anymore I just cant enjoy their story no matter what and only care about other couples in that manga.
F A C T S
Ahh yall seem to hate this manga alot bc of kou but i think it was really good. at least there was character development which is honestly rare for yaoi and the end relationship was one of mutual respect. The only thing I hate is the extra of them fucking in the office... Dodnt fit with the ending at all.