In his early days, Hiluluk was a thief who was diagnosed with a fatal illness. What he believed cured him was the serene vision of a grove of cherry trees. After being cured, he came to believe that there is no disease in the world that cannot be cured. He had a complete change of heart and returned to Drum Island, the island he was born on, to help cure a dire illness. Hiluluk's main dream was to cure the people on the island of their frozen hearts which had formed because of Wapol's selfishness. After Wapol declared any doctor not under his authority to be felons, he and Doctor Kureha were the only free doctors left. However, unlike Kureha, Hiluluk ended up doing more damage than good to his patients by accident.
He found Chopper one day while traveling home in a blizzard. At first Chopper tried to knock him away, but Hiluluk earned his trust by stripping naked in the cold, showing that he did not have any weapons or intention of hurting Chopper. From then on, the two slowly formed a sort of father/son relationship, traveling (and in a way terrorizing) the island trying to cure patients and generally resulting in them having to literally run for their lives from angry patients or their associates.
After one year had passed, Hiluluk reluctantly kicked Chopper out of his house, as he was going to die from his terminal illness. Hiluluk did not want his friend to worry about him. After Chopper learned the truth, he went on a journey for an Amiudake mushroom. Sadly, unknown to the reindeer, the mushroom turned out to be poisonous; but Hiluluk, who did know this, took it anyway because he was so moved by Chopper's concern for his well-being (Hiluluk had always called the jolly roger a symbol of vitality, which Chopper took literally, not realizing that the crossbones symbol in the medicine book he read meant that the mushroom was poisonous). Soon after, he realized that his 30 year-long experiment was finally complete, and declared that the country would finally be saved.
