 If you liked
Freezing
|
 ...then you might like
Gokukoku no Brynhildr
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The theme of young girls turned into super weapons is present in both manga series.
Both series features a regular main protagonist whose life is changed forever after meeting a certain female character. From there, they form a strange bond.
Both series has supporting characters who also has powers of their own rights. With that right, they do what they want but learn best to control them.
Both series has a lot of action, drama, some comedy, and violence. Both series features a darker tone as the series progresses where some psychological themes are introduced along with a dark story.