Nekopara

A game for sore losers who think beastiality was not enough. This game features four nekos who throughout the game get more sexually attracted to their master. Fun fact, the artist of this game is female, now that's rare for any hentai game. Eventually the nekos become your "catpanion" and miauw like a little bitch for sex every now and then.

It's very popular, so popular that there even exists an anime of it.