 If you liked
Kami nomi zo Shiru Sekai
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 ...then you might like
Tonari no Kashiwagi-san
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These mangas both have a main characters that is in love in the 2D world, but through some sort of complication they begin to interact with 3D women.
In the manga World God Only Knows it's because of a demon contract that Keima is forced to make women fall in love with him, but in Tonari no Kashiwagi-san one of the main characters, Yuuto, learns of a secret that Kotone had been keeping to herself, thus beginning the rocky relationship between the two.
I highly recommend the World God Only Knows to anyone who's reading Tonari no Kashiwagi-san since they both give off the same feeling and
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