A bit of Post Necromancy, but I feel I have to give this one a personal review. When I read this Yuri, it reminded me of a 4koma Futa involving Reimu and Cirno. I won't go into much detail, but it was a sad Lolicon.
This, however, was different. I don't know why, but the way you managed to word it made it feel like Kaguya was more like a Mother to Cirno, and that what she was doing was educating CIrno about something she'd have to decide for herself later...
*slow clap* Absolutely beautiful. I'd give it...5/5.