If you're looking for manga similar to Code:Breaker, you might like these titles. All recommendations are made by Anime-Planet users like you!
If you liked Samurai Deeper Kyo, you'll like Code Breaker and vice versa. Both being from the same mangak, you won't be surprised by the similarity in the design and the story telling. Both are about a young man at first looking like a dangerous person bearing an incredible power, but the main girl will be able to gradually change him and reveal that the main male isn't as bad as he seems to be. A lot of actions, awesome fights and great story telling.