Answer:
加 KA, kuwa(eru), kuwa(waru) - add, append, join, take part
機 KI, hata - opportunity, loom, machine
久 KYUU, KU, hisa(shii) - long (time)
介 KAI - shellfish, be in between
己 KO, KI, onore - self
They are the characters from which the following five katakana were derived.
カ Katakana "Ka"
キ Katakana "Ki"
ク Katakana "Ku"
ケ Katakana "Ke"
コ Katakana "Ko"