I was wondering if anyone knows of any recommendations for Western visual novels about hypnosis.

For hypnosis and not any kind of mind control and brainwashing, Penlight is probably the best one. It's not complete but the dev adds new content very often, the branching paths are pretty interesting and the girls are fun to mess around with.
It's just softcore though, as far as I remember, there's some nude scenes but no sex. The focus is on and the eroticism all come from the mind control itself.