[Fern]

The basic attack part of the Shinken skill from Soldier does not count for Black Drain from Black Knight, despite being a Soldier skill. The projectile part counts, though.

Tested by battling the debug Prinny from the arena and using Forced Move > Shinken (hitting it with the basic attack of it.)

[Neus]

Basic attacks don't deal skill damage, which is why it doesn't apply.