@Kanami-chan Well technically speaking yes it's yuri, he is transform into a girl. I can nitpick the TS considering the transformation is not definitive but maybe it will change later.
@Kanami-chan It is as far i'm concerned, he has the body of a girl. You can say it's a transgirl but that's still be Yuri since it's two girls loving each other.
Well Pixiv tags on the source said Yuri so i do think the author know better. As far as i'm concerned the witch love the girl form not the boy one so it's Yuri.
@igenetycs So by your logic two girls minds in two boys bodies is Yuri ? I hate myself for saying that because it sound stupid but it's the physical who count therefors it's Yuri not het and it have been Yaoi if Senpai was a boy and the Kouhai a girl genderswap into a boy.
@Lilliwyt Yes, I'd consider that yuri. Of course, it's different if they start to feel like they are the gender they swapped to (e.g. Kanojo ni Naru Hi), but the typical "I'm a horny 30 year old man in a 16 year old girl's body" is absolutely not yuri.
Somewhat related, I'd consider relationships between two women where one or both are trans to also be yuri (e.g. Aerial Magic), though that is exceedingly rare in manga.
This debate could easily be solved by distinguishing between Physical Yuri and Psychological Yuri.
Physical = Biological female or a post-op transsexual
Psychological = Female gender identity
So this is physical but not psychological yuri etc.