This one would be one of Mizore and Kurumu from Rosario + Vampire though age up a bit so they kind of have bit more mature feel, look towards their mothers for references on how that might turn out for them
Mizore's mom:
External
Kurumu's Mom:
Image
The actually pic itself I would love to Mizore lying on the bed naked and cover in lipstick kiss marks as Kurumu who is also naked is now eating her out. Cool?