 If you liked
D.C.: Da Capo
|
 ...then you might like
Kono Naka ni Hitori, Imouto ga Iru!
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-Both animes's setting/story goes by an omnibus format, and have small arcs for each heroine that doesn't diverge from the central plot of the story (with the setting intact)
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Recommended by MagicFlier
Both series contains a main protagonist who has several girls of various personalities interested in him, with one of them being a sibling in the series.
Both series contains a school like setting with comedy, drama, and romance.
Both series also a storyline that gets more complex as the episodes progresses with twists and angles.