Kamen Rider Kira

In Japan in 2013, Etsu Shimizu, a young man traveling alone in Yamanashi, met Mari Shinonatsu, a girl with a belt-like device. When the two met a humanoid gray monster, Mari, who owned the device but could not use the belt to transform, forced it on Shimizu, but successfully transformed into a "Kamen Rider" and seemed to trigger a certain trait in Shimizu... The story begins with this.