Basically, the teenage detective kiddo was frozen by some EVIL MASTERMIND PROFESSOR back in near-mid-1900’s, and gets unfrozen in the 2000’s by his (assistant's) granddaughter, Hikari. Hilarity ensues as he encounters weird new stuff and commits silly blunders in his daily life with Hikari.
A NEET by the name Oguni-kun refuses to come to school because there is nothing there for him, until an ambitious teacher comes to get him through his open window.