I think this is the third or fourth time I'm writing this so I'm going to make it short.
The opposite is canon. Hakdo already said in chapter 22 that he has no interest in having a relationship with Doochi (he's aware that it wouldn't work out).
Everything else is just something people assume because that's how every generic BL story with that kind of plot usually works.
BLESSED. THANK YOU! It’s very obvious that Hakdo has developed feelings for Sangho, regardless of his feelings for Doochi. Idk why people are worried, he’s not going to cling to Doochi he just has to go through this period of his life of moving on and falling in love with somebody else. I love this comic for being real and avoiding tropes and cliches. It’s honest and the characters earnest
The problem is not that Doochi is straight (it certainly is an obstacle but it isn't the reason why he has no interest in having a relationship with Doochi). He doesn't want a relationship because they have nothing in common and therefor a relationship between them wouldn't work (that's what he said in chapter 22) so even if Doochi gave Hakdo any signs that he might be romantically interested in him, Hakdo (most likely) still wouldn't start a anything with him.
Hakdo is aware it takes more to make a relationship work than just feelings.

I’m kinda sad thinking if Hakdo will let go of Sangho and will hold on to Doochi even more if Doochi gives even the slightest romantic interest in Hakdo.