Japanese verbs are placed into three groups.
This is the more complex of the Japanese verb groups because despite the ending being -u, the word can actually end in -su, -tsu, -ku, -nu, and even… -ru.
Some notable exceptions where a -ru ending is actually a ~u verb include kaeru (to return), hairu (to enter), shiru (to know) and iru (to need).
This group is often also called the -iru and -eru verb group because almost all -eru and -iru verbs are-ru verbs and not -u verbs.
Japanese only has two irregular verbs –
kuru (to come)
suru (to do).