
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.
Ojiichan wa Shounen Tantei / Ojii-chan is a shonen detective? / Ojii-chan wa Shounen Tantei / おじいちゃんは少年探偵 / 我的爷爷是少年侦探