 If you liked
School Days
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 ...then you might like
Code Geass: Hangyaku no Lelouch R2
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Both Code Geass R2 and School Days are psychological and thought-provoking animes involving a morally questionable main character who is surrounded by a bunch of girls who want a piece of him. (basically both are harems but SD is more open about it) Both also have two of the most shocking endings ever.