Go to the waterfall. We'll probably fall down into a palatial garden and Keene will end up failing the mission for harem-related reasons.
Sadly, no. We've run into a bit of a streak of strangely sensible choices...
...though Keene seems rather mellow about his impending demise.
Anyway, staying away from the raging death is the right choice.
And reunites us with both our buddy and the other set of options!