Bonchien Nicoli La Tasty Peach Uralis is the former prince of the Uralis Kingdom. He was raised with the expectation of one day becoming king, but his father ultimately deemed his younger brother, Torta, more fit for the throne. In an effort to prove his worth, Bonchien became obsessed with capturing the immortal being known as Fushi, spending nearly a year searching for him. He was ultimately able to locate Fushi not by his appearance, but by the spirits of the dead that always accompanied him, a sight unique to Bonchien.

In terms of personality, Bonchien initially presents as an eccentric and highly dramatic young man. He is prone to swift mood swings, bold proclamations, and emotional tantrums when events do not unfold as he wishes. He can be prone to speaking without considering the feelings of others and shows moments of cowardice that contrast sharply with his grandiose self-image. However, this flamboyant exterior belies a sharp intellect and a genuine, deep-seated care for the people of his kingdom and his own family. He is notably cunning and self-aware, having successfully outmaneuvered Fushi on several occasions and using his political influence to counter threats like the Church of Bennett. His primary motivation shifts over time, beginning as a selfish desire for recognition and the throne, but evolving into a sincere wish to help Fushi and protect others.

Bonchien's role in the story is defined by his unique abilities and his evolving relationship with Fushi. He is a spirit medium, possessing the extraordinary power to see, hear, and speak with the spirits of the dead, which he has been able to do since childhood. This ability allows him to perceive the ghostly forms of Fushi's past companions, like March, and even to see and converse with the enigmatic Beholder, whom he nicknames "Mister Black". This power is what initially allows him to track Fushi. After a series of conflicts, including being captured and nearly executed by the Church of Bennett for heresy related to his abilities, Bonchien fakes his own death with Fushi's help and begins living incognito under the alias Baron Springroll. His dedication to Fushi culminates in a pivotal act of sacrifice during a great war against the Nokkers, where he takes his own life to awaken Fushi from a helpless, dormant state. This act allows Fushi to take on Bonchien's form, granting him access to his spiritual powers and the ability to resurrect the dead and restore stolen memories.

Key relationships heavily influence his development. His initial rivalry with his brother Torta and his desire for his father's approval drive his early actions. He forms a profound bond with Fushi, moving from a captor to a devoted friend and ally who coins the concept of the "Immortal Army". He also shares a tender relationship with a woman named Todo, who is identified as his lover, and later adopts a boy named Chabo. Through his travels and hardships, Bonchien matures significantly. He sheds much of his childish vanity, coming to appreciate his life and using his remaining years to serve as his father's right hand and lay the groundwork for the charitable Tasty Peach Foundation, dedicating himself to helping Fushi and his kingdom. He is eventually resurrected in the modern era, living peacefully in Yanome as one of Fushi's revived companions.