That’s a tough one that’s split between Ayatsuri Sakon/Puppet Master Sakon, Onmyou Taisenki and Chiko: Daughter of 20 Faces.
Ayatsuri Sakon/Puppet Master Sakon has that Detective Conan kind of style to it but on a much grittier setting. Where one of characters gets beheaded by wire basically in front of the cast. There’s a very small cast they use similar to Kindaichi Case files in the small cast. The old art animation may drive some off but it’s as if Detective Conan or Kindaichi meets Death Note dark. It’s mid-long about 25 episodes if memory serves me. It’s a hard one to find to watch streamed as last time I had to watch in dailymotion but has now been makin rounds on youtube.
Other would be Onmyou Taisenki has a awesome catchy opening song that I love. (note: the english MV is only for mature audience I’m linkin the japanese ver.) The style of this one is similar to Rockman in that the main character gets pushed into a corner. Then his side kick comes to lend a hand and they bond. While they defend the world they grow closer. This series is longer about 51-52 episodes since it’s 2 seasons. Not as hard to find online stream as Sakon but have to work for it.
[Lovely fan made trailer by shinblanc]
CHIKO: Daughter of 20 Faces: Kaito Jeanne meets Robin Hood. The ending was a bit bland and felt like it didn’t close enough holes but I loved Chiko’s grit and how she grew as a character. The series didn’t make her a plain screamin Jane but she has some moxie to her and can hold her own. I believe this is only 21 episodes long sadly. There’s a few different titles to this anime so it can be confusing when searchin.
Music of the Night: Pulse by FAKE? (Japanese Ver.) – Onmyou Taisenki op 2