 If you liked
Zero no Tsukaima
|
 ...then you might like
Toaru Majutsu no Index
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Both involve the main protagonist becoming involved with a woman who comes from a world of magic, who then takes the responcibility of protecting the girl from the dangers to come.
the protagonists are very similar, index and louise are similar physically and mentally, since the two often end up hitting the man protagonist. Saito and Touma are also very alike. In both the anime protagonist must protect the girl from various dangers and both have magic, the biggest difference between the two is that zero no tsukaima goes on older and to aru Majutsu no index is in more modern times.