Average Jap-street look to me is:
Lightweight rims, usually white or bronze - Work, RAYS, Weds, Enkei etc
lowered on coilovers
strut braces
mildly tweaked brakes
Standard-ish interior except for:
one racing seat
Nardi 3-spoke deep dish steering wheel
a few gauges
2 DIN headunit, usually playing some dodgy hi-nrg J-Pop
rear tinted glass
vented bonnet - or the OE one, tilted up at the rear
a front splitter or mild bodykit
some stickers, maybe some for the
Fujiwara Tofu Shop
those regulation window stickers: 1 above the rear view mirror and the other at the back left on glass
the JDM sized plates
air cleaner
cat-back system
BOV (for turbo cars)
and depending on the car, the usual plethora of electronic gadgets like turbo timers, valve controllers, VAFC, SAFC, FC Commander blah blah
and depending on how authentic you wanna be: a cup-holder in the air vent, some ciggy butts in the astray and that red flare in the passenger footwell !