There are nowhere near as many guns in Japan as in the U.S., however they don’t not exist. (That sentence is dedicated to all the grammarians in the audience.)
There has been an increase in gun stories in the news lately and several shootings this past year. As far as I remember all the shooters were Japanese.
The story: Doctor Faces Charges After Son Dies While Kids Play With Rifle
The son that died was 2 years old. The son that shot him was 5 years old. The article doesn’t explain whether the gun was properly registered or not.