Who is profiting from selling weapons in Japan?

Nobody. Because the government doesn't allow civilians to buy them.

Pass that law in the states and you'll see a big drop in weapon sales.

Rinse and repeat in other countries.

>The gathered data shows the amount of arm exports

The data covers exports, not domestic civilian purchases.

Plus it's not small arms, like guns.

These are "major weapons", things like: aircraft, Anti-submarine warfare weapons, self-propelled and towed guns, Satellites, engines for combat ships, all turrets for armoured vehicles fitted with a gun of at least 12.7 mm calibre.