KUROKO and MIDORIMA listen attentively as you tell them that you are agender, asking respectful questions about how it is defined and what pronouns to use. They are both quick to assure you this new information does not change the way they feel about you, and spend time researching for themselves afterwards- moreso Midorima, who might not feel comfortable asking you too many questions outright, unlike Kuroko who finds communicating about subjects like this a lot easier.
AKASHI is very similar to Kuroko and Midorima; he asks questions about anything he doesn’t immediately understand, and is the quickest to adapt to the correct ways to refer to you. His only concern is that his father might not approve of your non-traditional gender identity and try to interfere, but his feelings for you are paramount and unchanged- if that becomes an issue, it is one that he will not back down on.
KISE, AOMINE and KAGAMI are initially confused by the concept of not having a gender, and you might need some patience when it comes to explaining the details. Once they understand, however, they’re completely on board and accepting. Aomine especially might slip up every now and then with pronouns, and accidentally refer to you as a boy/girlfriend instead of ‘partner’ or similar, but all three try their very hardest to change their thinking and speaking habits as quickly as they can to the correct terms.
MURASAKIBARA isn’t phased at all by your revelation; all that matters to him is that you still love him, because he still loves you. He can see that this is a really important thing for you though, so he does his best to show you that he appreciates your trust in him, pulling you into one of his bear hugs and even allowing you one of his precious nerunerunerune candies.
As much of a sadistic asshole as HANAMIYA is, you’re important to him so he’s on his best behaviour when you come out to him. This is, thankfully, one of the very rare topics that he doesn’t take as something to use as a weapon to tease or wound, because he knows that would be curtains for your relationship.