I wouldn’t call it a japanese accent, that’s a bit different, but ルール is the loan word for rule, approximated with japanese syllabary of course. So it’s ru-ru instead of rool. The r is also kinda rolled like a Spanish R, between and R and L sounds.
A japanese accent tends to have awkward stress-accent as well as R and L sounding too similar if not identical, and some general phonemes just not sounding quite right since japanese doesn’t have them (the ae sound for instance). Words that end in consonants can be tricky too, but japanese has a few in very casual speech (mostly by just leaving off the u in tsu) so that concept isn’t so foreign.
I’m so sad that he never went anywhere else with this himself, at least publically. Looks like there’s at least one team in Norway trying to take this concept to market though, hopefully they’re successful