Chaos;HEAd Promo with Anime Footage Streamed - Anime News Network
I linked to the ANN post here because it has english instruction on getting to the trailer. It look promising even if the art looks soso compared to the game.
Someone in the ANN forum said this was based on a doujin game despite the games credits being in the news article -__-
Oh and Clannad (TV probably) is licensed... maybe a thin pak someday..