Andrew Jin is a lone wolf. A hero so great, few have survived to tell the tale of his power. Aftoncorp's soon to be #1 Rider is…! A Liar. 

Really, he's just a kid who wants to be seen as stronger than he really is, holding a grudge on his older brother for abandoning him and fighting against Aftoncorp. 

He's not close with the others at Aftoncorp, either, all of them being significantly older than him, and hard to relate to. 

The only one he's really even close to is his partner, who is someone, er, rather, something given to him by William Afton, the CEO of Aftoncorp and his mentor. 

"Jake" as it calls itself, is seemingly convinced that it once was a human by the same name, having possessed the robot upon death. 

With his Stitching Blade, Andrew is able to "stitch" a Circket's form onto Jake, temporarily fusing him into Jake's body. 

And with Jake's lack of fighting skills, and Andrew's lack of vision while transformed, the two have to work together to be each others crutches as the stitched together rider: KAMEN RIDER STITCHWRAITH!