Changing to 1boy as the pixiv page clearly indicates this as otoko no ko.
That tag was added by a random user, not the artist. It shouldn't be regarded as authoritative. You can click the + at the end of the tag list on Pixiv to verify this; tags added by the artist have a lock symbol next to them.
The artist said nothing on Pixiv or Twitter to suggest that this is a boy, and as far as I can tell they have no history of drawing such things. I'm reverting the changes until someone can come up with evidence more substantial than a user-added tag on Pixiv.
Changing to 1boy as the pixiv page clearly indicates this as otoko no ko.
Dunno if you even played the game or know the story. Because most people already know that is basically Gorou's genderswap "avatar" done by a certain fox.