Ok, I just have to step in to give a neutral statement on the situation because people are either hating the fuck out of blue hair dude or feeling somewhat sympathetic for him. So here it's:
Whether or not he confess earlier won't make any differences because FMC has never see him as a potential romance candidate, she only see him as a friend. So even if he did confess earlier, it would just be the same result but with FMC probably just brush it off. What changes now is that FMC likes MC and vice versa, therefore she would instantly cut off any outsiders looking to step into the place she's saving for MC, just like in this chapter.
Another mistake he made was trying to force it onto FMC even after she stated her feelings (which is always a stupid move) and thus, instead of just getting rejected but still have a somewhat decent chances of continue being friends with each other if he know to keep his distance, he just damaged the friendship that they have had for years or just ruined it completely. Whether or not that friendship can be repaired is depended on whether he know how to properly admit it, let it go and maintain his distance, but due to how he has always taken other girls affections for granted as he has always been popular and as according to the bit at the end of the chapter, I would personally say that the chance is extremely low unless the author intentionally force it.
There, a neutral, rational, objective view on the whole situation, now we can put all of this aside and get back to some diabetically sweet and wholesome contents please.