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This made me genuinely curious, so I tried looking into it.

For one, holy shit, good luck finding anything besides travel spots for elderly people visiting Japan. Also some possibly racist "Japanese tricks" for "aging gracefully".

But once I started finding actual activities, uh... School, community services, and leadership roles for companies. Things that keep them physically and mentally active, and sometimes help bring in money. I couldn't find much on actual leisure activities. Looks to be a cultural thing, not remaining active in some way is seen as being a burden on your family.

Outside of that, I wouldn't be surprised if Pachinko was up there. It's already a fairly popular game, and if the parlors are anything like your average casino, the average age definitely trends upwards.