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As a disclaimer, I don't believe a system of "bases" is a good way to learn Japanese verb inflections. It seems to be a rather unnatural way to divide the language. As prime evidence, I offer up this explanation of an imperative inflection:

Contrary to what is stated above this writeup, an imperative inflection of a Japanese verb is not simply formed by this ending. Perhaps I should write a new Japanese Imperative Verb Inflection node, but for the sake of clarity of my argument, here is my understanding of the imperative.

Ichidan or Group I verbs, i.e. those ending with "ru", the uninflected stem of the word is attached to "ro". For example nageru, to throw, becomes nagero.

Godan or Group II verbs, i.e. those ending in a consonant + u, the uninflected stem is attached to "e". For example kaku, to write, becomes kake.

Kuru, to come, being irregular, becomes koi. Suru, to do, becomes shiro.

Also, desu in the conditional form becomes de areba.

Tasukete, stated above as the imperative, is actually the -te form of tasukeru, to help. The imperative is tasukero. The -te is a form that's often used as a shortening of -te kudasai, a request (please do ... for me). This can be seen by reversing the form using the rule above -- it becomes tasuketsu, which by a leap of imagination, could mean majority rule, tasuuketsu (a noun).