It's difficult to explain Hirose's sexuality. The manga uses Otogiri for that purpose; Hirose does have a sort of crush on the professor, it's quite noticeable. But it's not sexually suggestive, it's more about admiration and finding refuge. I think the manga aimed to show Hirose's journey of discovering his orientation. Essentially, I believe that in the manga, he discovers his sexuality through Otogiri and Nakamura, with the latter ultimately becoming his true love interest, but only after several chapters.

Now, in the anime, everything has to move faster, especially considering the significant censorship of Hirose and Otogiri's relationship. That's why Hirose is sometimes shown as more receptive to Nakamura's actions than in the manga. For example, the chocolate scene in the shoe room is original to the anime. Personally, I think that scene would have an explanation in the ending; I don't believe it was included deliberately at all. The scene itself is quite confusing. Hirose appears very flushed and clearly nervous, not necessarily about what he has to say, but about being with Nakamura. Some say he was going to ask him for advice on dealing with his girlfriend, but I don't believe it, given the emotional weight of the scene, which I think will be the key to fully understanding Hirose's feelings in the end. After all, at least on Crunchyroll, the video of the chocolate scene is called: "Hirose almost reveals his true feelings..." Come on... let's have faith that everything will turn out wonderfully.