Muma no Machi Cornelica

Based on the erotic doujin game by Dieselmine (ディーゼルマイン).

While working at a bar, the protagonist was asked to draw water. Upon picking up a mysterious stone he found there, he was whelmed by light. When he woke up, he finds himself in a country of succubi......! Various types of lewd demons draw near to him. He has to store a certain amount of magic energy in order to get back to his original world! What he will eventually face would be escape, or destiny to be a sperm slave forever...

(Source: DLsite English)