 If you liked
Darker than Black: Kuro no Keiyakusha
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 ...then you might like
Hakata Tonkotsu Ramens
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They give off very similar vibes. Urban settings (mostly at night), assassins, action, etc. Very similar jazzy soundtrack that really make the mood work well. They are also both about large organizations/cities that try to organize the characters. If you want something fun and exciting, while a bit ridiculous, these are both enjoyable.