 If you liked
Freezing
|
 ...then you might like
Hundred
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Hundred feels like it took the Freezing formula when I first started it.
Guy shows up to a school where women are the stronger force (Pandora/Hundred users) and the woman the protagonist follows is one of the strongest ones there (Kazuya to Satellizer, Hayato to Emilia) and has a little harem around them of women, but will always go towards their partner more no matter what and does have romantic elements to build the relationship between them. Both have a power where weapons form from energy implanted into bodies, and fight creatures from another world/realm.
If you like/love Hundred, you will definitely like Freezing.