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)