Nanjaro has a regular M-F job so he's only around his house on the weekends.

If you kill him from range while he's in slime form (for example by magic attack or a spell) then he won't transform into Nanjaro. Careful with King Yamada's Scepter too, if you knock the slime in a hole he won't transform either.

This stage is good for farming spells. Also, you can steal a Diamond with the Red Castanets from Nanjaro once.