I read a story in which a guy bought a cube off a late-night shopping binge and then ended up accidentally creating a harem. He eventually gets hired by the company that made them and almost loses all the girls because they lost their memories when the cube failed, but he was able to convince them about him and got them back. I thought I bookmarked it but apparently I didn't, so please help me find it! I can provide more plot details if needed, but I didn't want to accidentally spoil anyone more than I had to in order to identify the story...