
Hm, I'm not sure. It's also categorized and tagged as shounen ai. From my understanding, the category shoujo relates the target audience, not character gender. Now, the target audience may not be "shoujo", which would mean it's mislabeled. However, a manga can be both shounen ai and shoujo; they are not mutually exclusive. I hope this is helps!

u think guys dont like romance?

Bokura no Hentai was published in a seinen magazine, and its story focuses on transgender and cross dressing characters.
Seinen magazine anthologys publisher stories with from various genres and with varying content. For example: Saturn Apartments, Emma, Otoyomegatari, ES (Eternal Sabbath), Monster, Drug and Drop, Shimanami Tasogare, and Mahou Shōjo Madoka Magica were/is published in a seinen magazine.
https://tvtropes.org/pmwiki/pmwiki.php/UsefulNotes/MangaDemographics
Idk, though this is categorized as Shoujo, it's very Shounen-ai-- like BORDERLINE yaoi. Seriously, it takes one tiny step, and boom! It's a yaoi.
Part of me thinks this has been labeled labeled wrong...