 If you liked
Nanatsu-iro★Drops
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 ...then you might like
Senki Zesshou Symphogear
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Both these anime are similar in a way of how some characters interact each other in a way. They also both feature girls transforming and fighting, however Natsuiro Drops contains much more of an innocent feel to it. Lastly, the main characters in both series has a best friend who usually just stands in the background of the fighting, but tries to support them to the best of their abilities.