Denadu is one of the monkey priests who can be found in the Temple of Marimbo on Ape Atoll. He is one of the three priests that can be found there, along with Lofu and Hafuba. Like all monkeys in Marim, can only be understood with an amulet of monkeyspeak.
Unlike other monkeys, talking to him in human form will not cause him to call the guards, although he will call you a foolish human and say that "the Marimbo Guard" will kill you on the spot.