No it is not.
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.
paintball fields or on their property.
At paintball facilities, or their own property.
Paintball is not illegal in Japan. You can play at the related link.
Only if you own the property or have the owners permission.
The markers itself are not, but where you play may be.
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.
You can as long as you have the property owners permission, and as with anywhere you play paintball you must be 150 yards (450 feet) away from any public road.