But these are only a few. "Group 3" has two verbs, SHIMASU (to do), and KIMASU (to come). They conjugate irregularly. But they are just two. So, please memorize their conjugations. The dictionary ...

If you know what conjugation a verb exists in, you are more likely to work out how the verb is spelt or pronounced in different tenses, even if it is one you have not come across before.