It's a mutual crush! Aoi is completely oblivious to that fact though and thinks it's one sided, but they are both crushing on each other. Progress is kind of slow though, because there is a misunderstanding between the two making a romantic relationship difficult.
Spoilers below
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Despite the fact that the romantic aspect of their relationship is slow, the two of them have phone sex in one of the recent chapters, so that's some kind of progress at least LOL

People are worried this will become straight but I have bought and read 3 volumes in Japanese, these two do NOT get together. Aoi has a crush on his male coworker and Mebuku motivates/cheers him on in pursuing the guy. The whole manga is about the two motivating each other to make positive changes in their lives. Mebuku encourages Aoi to pursue his crush, and Aoi motivates Mebuku to stand up for herself in her toxic workplace by bribing her with stories of his sex life. Mebuku is aro/ace and has no interest in dating or having sex with other people, she merely uses BL (or in this case the content of Aoi's stories) to get off. We never see her masturbate though, it's just implied that it happens off screen. All explicit sexual content of this manga series is about Aoi and his male sex friends or his male coworker that he has a crush on.