Kakeru Yashio is a professional racing driver who competes in the MFG competition, piloting the number 16 Lotus Exige or Emiya. He is portrayed as an adult male with brown eyes and brown hair cut to ear length, often seen wearing a jacket typical of a circuit racer. Despite not sharing the same surname, he is the blood-related sibling of Nozomi Kitahara, and the two are collectively known within the racing community as the Yajikita Siblings. This sibling partnership is defined by their exceptional coordination on the track, where they specialize in advanced formation driving techniques.

In terms of personality, Kakeru is pragmatic and financially minded, often described as a "money man" who is keenly aware of the commercial and monetary aspects of racing. His motivations on the track are closely tied to his familial relationship. He has kept a close watch on the protagonist, Kanata, since the opening round of the competition. This close observation stems not from professional rivalry alone, but from a personal disapproval regarding his sister Nozomi's apparent attachment to Kanata. Despite this initial irritation, his pragmatic side surfaces in a surprising way; he is nearly convinced by Nozomi's practical, albeit unorthodox, theory that she should marry Kanata so that the three of them could combine their talents and earnings as the "Three Yajikita Siblings".

His role in the story is that of a consistent mid-ranked competitor. After the fourth round of the competition, Kakeru holds the 15th position in the overall rankings, having accumulated a steady performance that sees him frequently finishing in 12th place. His driving abilities are notable for their reliability and consistency, making him one of the few drivers alongside Takuya Yanagida who regularly achieves stable results in the unpredictable environment of MFG. He is also known to comment on the performance of his rivals, acknowledging the sheer speed and power of other high-performance machines such as the GT-R.