'One is One' is a new local term, that certain countries uses, to say goodbye.
Its something you won't hear often, rarely you'll hear it according to where you live.
It's not a popular phrase, but some people use it.
Joon: "Heading out! It was fun tonight
Joon: "Laterr, One is One!
Alexa:"yess one is one, see ya next time"
