When katu is used after a verb or other phrase, it's used like the spanish "luego" which is so hard to explain in english. It's kind of like, "then," as in this conversation that I remembered from the beloved classic Wayne's World:
Garth: Fine, go!
Wayne: I'm gone!
Garth: Go *then*!
This would be in Guarani:
Garth: Oima, eho!
Wayne: Ahama!
Garth: Eho *katu*!
Or when you thank someone from a store, they might say Nde katu. Don't try to literally translate it, it's just like an emphasis.
