"I were not to come, I would not see you"
That's what the -ku- is for in nisingekuona. It's the object infix for the singular you.
Nisingekuja nisingewaona should probably also be accepted as an answer to the English, because -wa- is the object infix for the plural you (also for they), and the English doesn't specify singular or plural. If it doesn't, next time I come across it in an exercise I'll report it (unless someone else gets there first).