Marulk (fan translation: Maruruk) is a delver that lives in Seeker Camp on the 2nd layer of The Abyss alongside the legendary White Whistle Ozen the Immovable. Despite his young age, he's already a Blue Whistle due to being a direct apprentice of a White Whistle.
At some point when he was very young, he fell down in an accident and nearly lost his life before being rescued by Ozen. Following the event, he chose to stay in The Abyss and become Ozen's disciple, but after some time, his eyes developed an extreme sensitivity to the light, so he never returned to the surface. He's in charge of the telescope inside the camp and is often keeping watch of the surroundings so that a gondola can be lowered when a delver shows up.
Marulk is a young boy with short blue hair and a rounded face. His feminine traits and maid attire leads people to mistakenly identify him as a girl, but he's actually a male. While the details are not clear, it's implied that Ozen was the one that forced him to dress like a maid.
He is a rather shy, but polite, individual who misses having the chance to talk with people of the same age because he manages the Seeker Camp. Though he does fear Ozen at times, he knows her well and trusts her.
He's very reluctant to talk about his clothing. When Jiruo mentioned it, Marulk became very nervous, despite greeting Jiruo as an old friend only moments before.
Seeker Camp Arc
Interested in finding out how two Red Whistles arrived to the Seeker Camp of their own merit, Ozen instructs Marulk to lend an ear to Riko and Reg in her stead; her reasoning was that it would be easier for children to talk to children. At Ozen's instructions, Marulk gives the two of them Blue Whistles; Ozen notes that it would be troublesome to explain the presence of two Red Whistles in the Seeker Camp, so for the time being they will wear Blue Whistles.
The next morning, following Riko wetting Reg's bed, Ozen walks into Riko explaining to Marulk and Reg what caused her to lose control of her bladder — a strange monster.
Later on, Marulk arrives in the middle of Ozen's and Reg's fight and is perplexed what caused it. Ozen instructs him to stay put and not to interfere. As the fight continues, one-sidedly in Ozen's favor, Marulk panics more and more, until he decides to disobey Ozen's order and hurries to get the other Subterranean Bandits to stop the fight.
Afterward, it's reveald that Ozen was trying to provoke Reg and Riko into a fight in order to test if they are ready to make theier way further down The Abyss. While she criticizes how Reg and Riko acted in the situation of conflict she praises Marulk, as he was the only one to take the right action in the situation; but also remarks that she will still punish him later for disobeying her instructions to stay put. After finshing her lecture, Ozen instructs Reg and Riko to stay three weeks in the forest behind the Seeker Camp as survival training. Reg and Riko return to the Seeker Camp after ten days and Marulk congratulates them on passing as most people don't even manage to make it even a week.
Ozen tells Reg and Riko that the training camp also should have helped both of them to train to keep track on time due to The Abyss causing a person's sense of time to get lost. Afterward, Riko and Reg leave the Seeker Camp to advance down to the 3rd layer and Marulk, with the rest of the Subterranean Bandits see them off.
Marulk has been trained in the basics of delving and displays enough skill and expertise to prove to be a Blue Whistle, despite his young age. As a direct apprentice of a White Whistle, he's considerably more skilled at delving than kids his age, and he is capable of surviving on his own in the less hazardous sections of the 2nd layer for at least a couple of days.
- His name comes from "marulk," the Swedish word for "angler."