Aki Japval was the son of Aki Japain. Both father and son were feared warriors. They were said to be invincible.
Father and son divided the coastal areas of Momogun between the two of them and they each protected their part of the coasts. They operated independently from any authority namely the Village Chief of Momogun. Their full time jobs were fighting intruders or pirates that ambushed the Momogun people at the coastal areas.
With their mystical invincibility and fighting skills said to be a fighting style of the Dayak Dusun (Momogun Laut/Sea Momogun), they kept the pirates at bay. The father and son team was a success.
One day, the widowed Aki Japain made a proposal of marriage to one of the women in the village. Unfortunately, it was the same woman that Aki Japval was in love with. Aki Japval was heartbroken. Nonetheless, he gave way to his father. To nurse his broken heart, he left the village and wandered into the Tampasuk river area.
The Tampasuk area was often attacked by headhunters. Hence, he decided to venture to this area to nurse his broken heart. What better way to forget your pain than to have a good fight or fights.
When Aki Japval arrived at the Tampasuk area, he was attacked by the locals because they thought that he was one of the headhunters. However, Aki Japval did not retaliate and passively continued his journey. He didn't have to worry about injuries because he was invincible, any spear attack would just bounced off his skin. Eventually, seeing his behaviour, the locals decided that he was just passing through. Hence, they left him alone.
Aki Japval settled down in one of the areas near the Tampasuk River and he married a local woman.
One day, the spirit that look after his family came to him in a vision and told him that he had to return to Kudat immediately because one of his family members was dying. He did so and while he was back in his village, he told him family of the new live he found at Tampasuk. They were happy for him and gave him their blessing. Aki Japval eventually returned to his wife and the people of Tampasuk.
Ever since Aki Japval took residence in the Tampasuk area, there were no more attacks from headhunters due to his presence.
Legend has it that Aki Japval became an independent leader in the Tampasuk area which happened to be a Momogun Rungus area also. Perhaps it became his independent Chiefdom but we would never know.
Source : Momogunology Research Centre