Detective Conan, Kamisama no Memochou Recommendations
Bot these shows have a great mystery set up. They both have smart, but physically restraint heros. Conan has a deeper story and better mysteries, but Kamisama is a fun watch bringing more personality to the characters at times. kamisama's mysteries arent as deep and difficult as conan's but that can also work to its advantage because you feel like you can "win" more often watching it as well. If you dont mind the loli and schoolgirl like giddyness, kamisama is a great show for anyone craving more mysteries.
Both series feature young detectives, but "Kamisama no Memochou" breaks from the norm as the detective is female instead of male.
Both are on detectives
Both detectives are young teenagers .. well sort of ...