Pretty much all data plans in Japan since last year are data capped. Of course you get unlimited but the speed is capped to Excruciatingly Slow after 7GB (on the higher end plans).
EDIT: you can get unlimited WiMax boxes (capped at 3 GB/3 days), but that doesn't work in a lot of areas (Tokyo subways...). Some MVNOs seem to offer unlimited data but it's speed capped from the outset.
EDIT: you can get unlimited WiMax boxes (capped at 3 GB/3 days), but that doesn't work in a lot of areas (Tokyo subways...). Some MVNOs seem to offer unlimited data but it's speed capped from the outset.