A guy finds out that girls from another world are after his semen. He later finds out that the cause for this is that an AI created a game which merged into reality and the girls from another world are promised a great reward if they bear his child.

I'm pretty sure I've mixed up some of the details, since my memories of the series is not very clear but anyone who has seen anything similar should please help.

Thanks.

Hi guys, I finally found the title. It is All intruders crave me, just for those who might get interested.

Thanks to all who posted earlier.