Canon aromantic and asexual character, possibly agender, but it's not confirmed, it is believed to be so since it is based on the writer that is ace, Aro and agender.
It's the main premise. Canonically ace with the word asexual explicitly said, even in the synopsis. Author recognize that aces can be alloro or aro (remember: in Japan, if not specified, Ace usually includes Aro, just like bisexual also implies biro antic if not specified)
Ch. 44.5 two aroaces fake date. One shot.
Canon alloaro ML
Canon aroace character, the word is not used but it is clearly explained
Canonically ace MC, but likely aroacespec
Canon aromantic character. Teacher Sasaki opens up to student abou not feeling romantic attraction:
"I've never felt romantic feelings for someone, that's how I've always been up to now and I don't expect that to ever change"
Canon asexual character. Speculated to be aromantic
We really got here huh? Canonically ace (I mean he is still figuring out but the word is there) and heavily implied Aro (I think it's just that thing of people thinking ace = aroace)
Canonical Aromantic (explains his feelings, doesn't use the word).
Minor character, shimotsuki shows up on ch. 3, and on ch. 7 explains he never felt love for men or women and doesn't think he ever will but still have things he likes otherwise. Author also uses the term "romantic attraction" regarding the main couple, which makes it more likely that this is written by someone who knows the a-spec community. (also has a nice bit talking about lgbtq+ rep)
Shimanami Tasogare