 If you liked
Death Note
|
 ...then you might like
Ouroboros: Keisatsu wo Sabaku wa Ware ni Ari
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Admittedly, Death Note and Ouroboros are only similar at their core; they are both dark crime-drama manga series. However, both maintain this core really well. While Death Note uses the supernatural to explore man's dark nature (as well as its flawed protagonist), Ouroboros has realism and seinen-maturity on its side to do mostly the same. If you liked Death Note's atmosphere, Ouroboros would be a good fit.