Tetsushi (a 5th grader delinquent who rules over the students of Jouin elementary), Ryuuchin (Tetsushi's right hand man) and Tsuda (their sometimes-ally), are known to everyone in town as the "three evil prankster kings."
In a creepy pharmacy located out-of-town, the boys meet an old man who bestows a strange and other-worldly power upon them. Soon after, our 3 young pranksters find themselves battling a variety of ghosts and demons...!?
(Source: M-U)

Newly-instated detective Ishida Tomohiro returns home one day to find a naked man in his house. He asks Tomohiro to identify himself, only to vanish into thin air before the startled young man can come up with a response. Soon afterwards, Tomohiro becomes tangled up in an odd situation involving a killer sword that can possess people. Then the same guy shows up again: this time fully clothed and actually physically present. "Kyousuke" is a member of the supernatural task force affiliated with the police, and Tomohiro ends up being transferred there. Now he'll have to handle all sorts of bizarre and out-of-this-world situations alongside his extremely quirky new colleagues!

Source: Baka-Updates

This is an adaptation of the first instalment of Kouzuki Hinowa's two-volume light novel series, Keishichou Seikatsu Anzenbu Yuugeki Sousahan.