On Pixiv, it's tagged with "男の娘", or "otoko no ko". Now, when using the kanji 子, "otoko no ko" means "boy"; I can't find what 男の娘 means, other than loose translations that say "daughter of man". I'm sure it's some sort of pun, perhaps used to denote a cross-dressing boy, but I thought I'd bring it up in case anyone wanted to clarify the tags here.
I'm not able to answer your question fully, but this is definitely tagged with the crossdressing tag, so switching from futa to something more appropriate.