An Umbra Hand with the personality of a friendly, reliable older brother. Compared to Bondrewd and the other Umbra Hands, he is noticeably tall. He served as Prushka's mentor, and her way of speaking was influenced by him. He refers to Bondrewd as "Boss" and always speaks in a casual manner, suggesting he holds a high-ranking position among the Umbra Hands. He was responsible for raising Prushka in the past. According to Prushka in chapter 73, he apparently made a living as a "con artist" before joining the Umbra Hands.

A scientist dedicated to research at Ido Front. He frequently says "Oya oya" and "Subarashii" (Marvelous). Although a newcomer among the White Whistles, his achievements include preventing large-scale insect infestations, opening previously impassable routes, securing bases in the deep layers of the Abyss, developing new medicines and complete nutritional foods, and investigating the conditions and symptoms of the Curse. He is not one to rest on his laurels; he is a soft-spoken philanthropist. While he appears to be the most gentle of the White Whistles introduced so far, his true nature is like that of an alien whose values are incomprehensible to ordinary humans. The ultimate proof of both his brilliance and his abnormality is his invention, the "Cartridges."

An Umbra Hand clad in death-shroud-like gear who incinerated the Garden of Unyielding Flowers in the fourth layer after it became a nest for Kuongatari. Due to his equipment, he always maintains a slightly hunched posture. Known by the moniker "Gyaryke of the Ash," he uses a flamethrower as his weapon. According to Kravari, he is a "flame bastard." According to the author, his strength is roughly on par with Bido (meaning he is quite powerful). Before his name was revealed, readers often referred to him as "Garden-san."

A lively, strong-willed, and reliable girl with a powerful sense of adventure. Her exact age is not revealed, but based on scenes where she blushes saying "I'm at that age, you know..." and Bondrewd telling her she is "almost a grown lady," she is estimated to be slightly older than Riko (around 13 to 15 years old). Though not as reckless as Riko in aiming for the deepest layers while still a Red Whistle, she takes on various challenges such as exploring dangerous areas within Ido Front and assisting with Bondrewd's experiments. She is Bondrewd's daughter.