It seems you might be referring to "Kamen Rider Gaim" or perhaps "Kamen Rider Grease." However, there isn't a series specifically called "Kamen Rider Gavv" in the Kamen Rider franchise as of my last update in October 2023.
Kamen Rider is a long-running franchise in Japan featuring various "Riders" who fight against evil forces, usually using unique belts and often with themes related to insects, animals, or other motifs. Each series typically