ADJECTIVES ALWAYS END IN A DIPTHONG OR TWO VOWEL SOUNDS TOGETHER. they can end in -
ai, ei, oi, ii, ui,
The adjectives ending in ei somehow came to be irregular and don't follow the nice pattern set up for us by the other vowel comination endings.
akai, kirei, aoi, utsukushii, atsui
akai ending in ai
kirei ending in ei
aoi ending in oi
utsukushii ending in the double ii
atsui ending in ui
These are in the order of the syllables a i u e o
In like manner when we add + ku + naru to the stems of adjectives we have a grammar that becomes the adjective. They are set up to become verb bumpo like
akakunaru, even kirekunaru, atsukunaru, aokunaru - its turning red, pretty, hot or its turning blue,
okikunaru- its growing larger or getting bigger"