Ending of plain verbs
This is going out on a limb, probably just desperate at this point, since I struggle remembering vocabulary and my mnemonic creative skills aren't great.
Is there any particular reason why plain form verbs have the ending they do?
行く
見る
返す
etc.
Why ku in iku, why not iru or isu? I know they mean other things, and it's probably to do with what sounds best, but I'm wondering if all verbs that end in ku are similar to each other, and different to those ending in ru, which are different to su, etc.
Many thanks in advance.