Honestly, I'm going to have to disagree strongly on the 'obviously'. For instance, presented as it has been to us, it presently also has the potential to be something much sadder—someone deep in depression with heartbreak, trying to make themselves be what the person they love wants, because they feel (accurately or inaccurately) that they can't be accepted as themselves.
Or they could, indeed, be trans. Or they could just as well be a cis-male cross-dresser who's hopeful about the options being female-presenting currently affords them, and the half-year-off was only tangentially-related depression and/or heartbreak—there's a lot of options here, even if some of them are much more likely than others.
(I have a pet peeve about people who categorize everything that 'looks' trans on the outside as 'definitely trans'. That's the same sort of putting-people-in-boxes based on superficial stuff, that all this nice queer stuff was supposed to get us away from, at least a little...! But we really like putting people in boxes!)
To be clear, all that said, thematically, them being trans is the most likely. Like the line(s) that the title chooses to emphasise definitely resonates as a trans message; "you're not going to get a next life, so be the gender you want this one". The choice to point out the staff bathroom in passing stands out, too. But that's all suggestion, not stated fact—it's not for instance yet to the point where I feel compelled to look up what current mangadex genre-tagging policy is for trans stories is to see what the official rules are in that case. Which is just as well because the dudebros running this site usually infuriate me with decisions on things like that. XD
Yeah, I don't care whether he is trans or not, the main point is he wants to become a girl and likes the guy. I'm just happy knowing that, can we get the next chapter already, pretty please?