Bana the betrayer - How to get the quest?

It is often needed to talk to a certain named NPC first, before a new quest will pop up.
For Example, Emmy's quest where she wants you to collect a shield or a sword for her is only triggered, when you talked to the general first.
So, walk around Nopon Village and talk to every named NPC.
Since Bana is supposed to be at the lake on top, try there to talk to people. Maybe they'll initiate the quest. But that's just a guess.

If you haven't triggered the quest after alcamoth lock out, then you're out of luck, since part of the quest need you to do something there. That's why it's a series of timed quest.

I have just finished the quest just before this one and Alcamoth hasn't been locked yet but still no quest. Does it have something to do with the story line? I've just unlocked the seals to Prison Island do I have to continue until I get the quest?

You have to progress the story to the point where Alcamoth is locked out before you can get the quest.

Does anyone know exactly how to get this quest? I saw in the guide that one of the rewards was an exp up vi and I would like to have that.