"Bishoujo" (pretty girl) games are a genre treated in western media like a thing for perverts and otakus. While that in part is true as it's often mixed with "eroge", they're actually very entertaining if you love to read and, of course, know Japanese.
"Hentai" games are not my thing, however I like "Ecchi". People often define "Ecchi" as "cock tease", not far from reality. But apart from that distinction between "bishoujo" game types, they're really curious about how interactions between an stereotyped anime girl and the player work. More than the usual "cock tease", the interaction itself gets to the point it turns quite hilarious and fun. One of my recent favorite games ("Dream C Club" which I'm playing now on PSP) is getting the Mahjong treatment.
I do have to wonder why from the many scenes the video has, it had to show precisely that one.