Kaji's father was a salaryman, who raised Kaji on his own as a single father - and despite his often overwork, it wasn't as if Kaji made life any easier for his father with his penchant for causing trouble and getting into fights in school. Eventually, his father would sadly pass away when Kaji was still rather young - only thirteen years old - and he ended up having to live with his Grandfather. Despite his father having planned to leave an inheritance for Kaji, he wasn't yet old enough to get the money so it didn't come through just yet. Living with his Grandfather was somewhat rough at first, as the two clashed often, but eventually Kaji discovered his Grandfather - who he knew flew fighter planes in World War Two - was one of the first Bosozoku, a Kamikaze pilot turned motorcyclist in search of the thrill he once had as a pilot, and they managed to get along pretty well from there with Kaji learning just about everything he could relating to motorcycles from his Grandfather, despite his uh... below average performance in academics. After his Grandfather passed away later on and he was old enough to recieve the inheritance from his father, he used a good portion of the money to buy himself a proper motorcycle - a Yamaha VMax - and joined up with a biker gang of Yanki, having made the prior connections needed to do so in his time in school, despite never graduating. In his - admittedly thus far somewhat short - time as a Yanki, he's already made quite the name for himself as a brutal - though certainly hot headed - fighter and a daring motorcyclist who often takes some of the craziest risks, much to the amusement of his Yanki comrades.