[yongjik]

In Korean there are four commonly used forms, which map into the combination of (formal vs informal) x (polite vs not-so-polite). (That's a simple picture and the reality is a lot messier... but let's not get into that.)

E.g.,

Formal polite: military, business email, public announcement

Formal non-polite: textbooks, novels

Informal polite: kids' books, between coworkers, between customer and clerk

Informal non-polite: siblings, childhood friends, mom to kids

[BalinKing]

This sounds very similar to my (very amateur) understanding of how Japanese works as well.