Current policy is to tag Bridget as male unless physical evidence in the image proves otherwise, including the presence of the transgender flag. Non-bodily evidence (e.g. transgender flag) is only relevant to Rating:General posts.
In practice, the Rating:General requirement means Bridget should not show hints of male anatomy, including bulges. If you crop everything but a fully-clothed Bridget from the image and the cropped image qualifies for G, the original post should still qualify for 1girl even if there's an orgy (without Bridget, of course) in the background (I'm stating the obvious because some users will definitely take the G rating part of the statement too literally; the statement could probably benefit from a rewrite).
This post meets the transgender imagery criterion, but not the SFW criterion. And there's no evidence Bridget has a female body here, which futanari and newhalf both require. In fact, the transgender flag is evidence against her having a female body in this case. The pronoun in the commentary also does not indicate she has a female body. After all, transgender people are addressed with their preferred pronouns by those who acknowledge and respect their gender identities regardless of whether or not they get physical sex changes.
Thus, under the current policy, 1boy and otoko no ko are the correct tags to use for this post.
