Ok ok i think i understand whats going here! I was revisiting the whole series for a little animatic/edit i was making and i realized... Hiranos asexuality shows through those physical romantic tests Kagiura proposed. Hirano doesn't feel attraction, doesnt have the interest in engaging in so, hes just happy to see Kagiura happy. But hes clearly inlove, seen by how he does things he doesn't do to others unconsciously, he doesn't want to separate from Kagiura even if it means experiementing things hes not interested in. He blushes at Kagiuras praises and is annoyed when hes not satisfied with what hes giving. The moment of "if touching you makes you happy, then look happy when i do it!" Is what settles that for me, Hirano is an asexual who loves through acts of service/gift giving, why would he waste time doing something hes not interested in doing, if the person hes doing it for doesn't like it either?
Also, in this chapter he realizes, hugging is not working for him, because its Kagiura triyng to make Hirano feel the same butterflies as he does, but thats just not what he wants, he doesn't really feel physical things like that. So he tries to hug him instead, and realizes, thats what he enjoys, to see Kagiura happy in a way that hes not the one being given that attention.
Thats my interpretation of his character, and i hope what i said made sense ^^