The Three Charms R - The Twelve Monster Girls of Mahoroba

For some reason, the protagonist has got to live in the "Youkai Mountain".
Which means he is always targeted by monster girls that suck man's lifeforce...

Tentacles, slimy fluid, art of brainwashing...
The monster girls seductions that incorporate magic
will gradually grind down the protagonist's will...

Sometimes their acts of cumsuckery come with verbal abuses...
And at other times he is courted and generously forced into "male-female relationship"...