 If you liked
Zero no Tsukaima
|
 ...then you might like
Oda Nobuna no Yabou
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Both series is about a high school boy who is transported to a different time period or world and are forced into serving girls who are big time tsunderes and may or may not like each other.
Oda Nobuna no Yabou is an alternative history where most historical figures are of the opposite genders.
Zero no Tsukaima is set in a fantasy world with magic and mythical or strange creatures.