One of the hottest things I've ever eaten was at a Korean-run Japanese curry house in NYC.
IIRC you chose spiciness on a 1-5 scale. The first time I tried a 2 and it was damn spicy. Next time I tried a 3 and it ruined my lunch, my pride, my afternoon, and my evening.
There are plenty of curry places in Japan that do spice levels too.
However normal Japanese curry tends to be pretty mild as well as other food in Japan, including Japanese style Chinese places which often serve dishes like mapo tofu with no spiciness whatsoever.
There are Japanese curry places in SoCal that charge extra (~25-50c per level IIRC) per spice level. Since I couldn’t handle any more than 2/10 I found that a win-win :)
IIRC you chose spiciness on a 1-5 scale. The first time I tried a 2 and it was damn spicy. Next time I tried a 3 and it ruined my lunch, my pride, my afternoon, and my evening.