 If you liked
ChäoS;HEAd
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 ...then you might like
Kami nomi zo Shiru Sekai
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Main character is an otaku gamer. He hides from real world in anime-related games: dating sims and eroge. While the story line develops, he meets strange girls with mystery powers. World of games and real world mixes in weird way. Both anime are harems but have a very few number of ecchi elements.