I get what you mean, though I think in this case Shion is too much of a man - as in it is his gender identity no matter what he looks like - to want to remain looking like a woman, even though it will be harder on them (also I believe he discovered some of the "fun" parts of looking like a woman in every day situations and he would rather live as a gay man than an heterosexual woman ╮( ̄▽ ̄)╭)
Sure you could tell them the truth, but I think it's a bit of a stretch to say he's trans. Bc even when he's in the female body he still views himself as male. Personally, as a non-binary person, it just doesn't sit right. The amount of gender dysphoria that he will go through will be traumatic. Ofc this is a personal opinion and others can and will think differently.
personally i whould chose to stay a girl, it will be more easier to live my life with someone i love without being scared of people saying something