Speak to Kerutoto inside the Rhinostery and make sure you get the right Cutscene, since she starts a couple of other Quests. The correct cutscene starts with "Have you talked with Leepe-Hoppe on the second floor?"
If she continues to give you the cutscene for Diabolos, accept the quest and talk to her twice to activate the cutscene needed for this mission.
Longer route: Head to the Temple of Uggalepih in Yhoator Jungle (J-11). Enter the Temple and head down the stairs. Once reached to a T intersection (J-7), turn left (i.e. North) and pass through the "Granite Door". Go North to (K-3) and zone back out into Yhoator Jungle. Once in Yhoator Jungle, go down the hallway until it opens up, take a right until you see a similar Hallway to the one you just came out of and zone back into (F-7) of the Temple of Uggalepih there. On this map, everyone needs Invisible, the safest way would be to use Prism Powders, since the Magic Pots there aggro to Magic. Follow the path, take a left at the first intersection and a right at the second, leading you down some stairs and to a door ahead of you. Behind this door is the room Bonze Marberry spawns at J-9 on this map.
His most dangerous ability is Everyone's Rancor, dealing 10x the DMG of the ordinary Everyone's Grudge Tonberry attack, or 50 damage per Tonberry killed. This attack will be used once, immediately when Bonze Marberry falls below 25% HP. If it is casting a spell during this time, it is possible to quickly defeat the NM and not see the attack used. The attack can also be prevented via an attack of your own that's strong enough to take it straight from over 25% HP to zero.
If you have to fight Tonberries on the way to the NM, make sure you Call for Help to avoid increasing your rancor. You can also clear Tonberry rancor with the quest Everyone's Grudge.
The NM can be pulled to a safe fight at the corner of the room avoiding the other Tonberries once you kill the Magic Pot. The Magic Pot can also be pulled through the door by casting a spell close to the door.
The NM drops two Cursed Keys per fight. Every Windurstian on the mission must have one to continue the mission, so the party must wait for respawn if needed.
If anyone in the party needs Carbuncle Mitts, now would be a good time to receive the necessary item to spawn the NM that drops the mitts. The side rooms in the Hallways before and after the NM Room might contain a ???- check it to receive an Uggalepih Offering to trigger the Carbuncle Mitts NM.
Once everyone has their keys, head through the northern entrance to this room, take a left at the intersection and find the Granite Door at (J-6). Trade the Cursed Key to the door and get a cutscene with Rukususu. You will lose your Cursed Key after you trade to the door.
Rhinostery minister Rukususu has traveled to Elshimo to investigate the facts concerning Iru-Kuiru, a researcher from thirty years past. The Rhinostery has asked you to bring Minister Rukususu back for her own safety.
SPOILER WARNING: Click here for additional details about this story line.