Popp is a fifteen-year-old magician and one of the central figures among the group known as Avan's Disciples in Dragon Quest: Dai no Daibōken Buchiya bure!! Shinsei Rokudai Shoguo. He is an ordinary boy from the remote village of Rankaksu, the only son of the weapons merchant Junk and his wife Steine. Fascinated by the hero Avan when Avan passed through his village, Popp left home almost as a runaway to become Avan's self-styled apprentice. By the time the story begins he has already trained under Avan for more than a year, and he accompanies his master to Dermline Island, where he meets Dai and becomes his senior disciple.

At the start of his journey Popp is a coward. Faced with opponents stronger than himself, he readily loses his nerve and thinks only of escape, and he is even willing to abandon his friends in moments of danger. He is also boastful, sharp-tongued, and easily distracted, with a lecherous streak that often places him in comedic situations. His early reluctance to fight for anything other than his own comfort earns him disappointment and scorn from those around him, especially from Maam, whose criticism and disdain become a turning point for him. Gradually, Popp learns to summon a small measure of courage: he throws himself into battles he cannot win for the sake of his friends, and his decision to stand alone against the beast king Crocodine, knowing he was outmatched, impresses even his enemy and marks the beginning of his real growth.

Popp's motivations develop from self-interest to deep loyalty. He is driven above all by his bond with Dai, for whom he becomes the closest friend and most trusted partner. He is also motivated by his love for Maam, by respect for his two masters, and by a growing sense of responsibility to protect his companions. Over the course of the story he becomes the party's vanguard and morale keeper, the one who steadies his allies and pulls them forward. His quick mind matures into genuine tactical brilliance: he becomes skilled at provoking enemies, drawing them into traps, and reading the flow of battle, and he eventually plans strategies clever enough to surprise even the Great Demon King Vearn.

In the broader story of the group, Popp serves as the party's magician and later its great sorcerer, and he is the character who most closely represents an ordinary person rising through effort. While his companions come from royal bloodlines, legendary parentage, or rigorous combat training, Popp is simply a weapons dealer's son, and this difference becomes a source of private suffering for him. When the five Avan's Disciples attempt to light their sacred stones for the Minakatoru spell, Popp alone fails, and he sinks into despair, believing he has no special strength of his own. His awakening comes when Meiru, who secretly loves him, is gravely wounded while protecting him. Moved by her plea, he confesses his love for Maam, and in that moment his soul power of Courage manifests, his stone shining green. The awakening dramatically expands his magical ability, allowing him to use healing magic he had never mastered and to save Meiru's life in an instant. From that point he no longer compares himself bitterly to others and embraces the identity of a great sorcerer rather than a sage.

His key relationships shape much of his development. With Dai he shares an unbreakable friendship built on trust, mutual sacrifice, and playful bickering, and Dai relies on him for support in ways he grants no one else. His feelings for Maam run throughout the story; he treats her with teasing and rivalry, but his love for her is evident to nearly everyone but himself. He regards Hyunckel as a rival for Maam's affection, yet deep down he respects him as a senior comrade and fellow disciple of Avan. With Leona he develops an easygoing friendship, calling her casually and trading insults with her despite their awkward first meeting. Meiru's devotion to him goes unnoticed for a long time, and his two masters influence him profoundly: Avan inspires him to become a hero's apprentice, while the great sorcerer Matoriv subjects him to harsh training and teaches him both spells and the discipline of a mage, eventually calling him his proud disciple.

Popp's growth is both personal and magical. He begins with fire spells of the Mera line and ice spells of the Hyado line, and he shows unusual talent in the fire family. Under Matoriv's teaching he trains relentlessly and masters Medoroa, the supreme annihilation spell developed by his master, which combines fire and ice energy into one of the most powerful spells in the world. Over time his magical reserves grow to several times those of an ordinary mage, and he gains the ability to weave multiple spells at once. He also performs astonishing feats of will and sacrifice. When Dai loses his memory and is on the verge of being taken by Baran, Popp deliberately plays the role of a hated enemy and sacrifices his own life with the spell Megante to shock Dai's memory back. Even in death his lingering will allows him to strike Baran with magic, a miracle that shakes Baran's view of humanity and helps bring about his revival through dragon blood and divine tears. In the final confrontation with Vearn, Popp single-handedly cracks the enemy's ultimate technique, the Heaven-Earth Demon Combat Stance, by using the mirror entrusted to him by the fallen knight Sigma, and he even tears apart the Kaiser Phoenix with concentrated magical power, terrifying the Great Demon King. Enemies who once dismissed him come to regard him as the first one who must be eliminated, and the Demon King's army eventually names him the most fearsome of Avan's Disciples. Despite all this, he remains the same plain-spoken, emotional young man at heart, and his story is one of an ordinary person who becomes extraordinary through courage, friendship, and persistence.