There is no registration or background check for paintball.
Yes, without permission.
Paintball is not illegal in Japan. You can play at the related link.
The markers itself are not, but where you play may be.
It is Illegal to play paintball inside city limits, unless you are at a legitimate field or have a large (enclosed with proper net) private property.
Definitely not (thank goodness). I own 2 paintball guns and play at least once a month. There are plenty of fields; paintball is very prevalent here.
In any woods you own, or at a public field. Anywhere else is illegal.
paintball fields or on their property.
people who play paintball play because some of them want to be in the military or law enforcement or to experience paintball
a paintball arena is an indoor paintball field where they usually play speedbal