Ji-chan Jet

is a Japanese light novel series written by Keisuke Hasegawa, with illustrations by Oka Asaha. The series began publication on March 10, 2005 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
My grandpa is young. It's too young to be possible. Even though I'm about to reach the 60th birthday, I have red hair that stands out, I love the guitar, I wear vintage jeans and leather bread, and my whole body is full of silver accessories. It's funny at all. It's too funny. I mean, why are you so young? Because, no matter who you look at, my grandfather is a "young man" around the age of 20 ...!?