Just going through looking up gender-bender titles today, and I saw the tags discussion. For the record, none of the "X-Change" series lists trans in the tags, and neither do "LoveChange," "Suddenly Feminized?! School Survival," or "Shinobu-kun, the Only Girl at Boys School." Some of them have descriptors written in that are not official tags, including "futa" (by itself, without the trans) and "transformation (M2F)." Some of them list both male protagonist and female protagonist, but none of them are labeled as trans. Gender-bender would be the appropriate tag, if there was such a tag. The point is, gender-bender stories are not a new thing, and traditionally they have never been given the trans tag.
Adult games that have a real story and are meant to be suitable for fapping have to walk a tricky line sometimes, but in this case I would argue that both the story and the imagery make it inappropriate to tag as trans.
From a story perspective, someone who has always been male and was happy that way being forced suddenly into a completely female body is a very different character (as regards their mentality, emotions, and goals) from someone who never felt entirely comfortable in their physical birth gender and either has gone through or is currently going through the long process of having their body altered to match their mind.
From a pure "searching for porn" perspective, people looking for trans porn are looking for people who look mostly female but have a penis. From what I can tell, no such character exists in this game.
On the game itself, I have to say that for a game where a pure boy transforms to a pure girl, the MC looks needlessly androgynous. I'm actually not sure which pictures it's supposed to be a boy or a girl. That strikes me as an issue for this genre of game, and it might be coincidentally making the whole "is this trans" debate more confusing for people.
