I'm relatively new to the scene, but here is what I can verify so far as clusters of under 25 Korean girls go.
Diamonds at Kennedy and Finch
Markham Oasis at Esna Park and Steeles
Studio 9 near Keele and Eglington (highly recommended)
www.toronto-exotic-massage.com
will give you the location and phone numbers
Let me know if you know of any others