Gugu begins his story as a hardworking young boy living a difficult life with his older brother Shin in the city of Takunaha. The two brothers work as servants and farmers, saving their earnings in the hope of one day building a house together. During his time selling vegetables in the marketplace, Gugu frequently notices a wealthy girl and develops a quiet admiration for her. After returning her lost dog, the girl, whose name is Rean, gives him a valuable ring as a reward.

Gugu's life changes dramatically when a log falls from a cart and begins rolling toward Rean, who is picking flowers at the bottom of a hill. He pushes her out of the way, saving her life but suffering a catastrophic facial injury when the log crushes his head. A man known as Booze Man, an infamous alcohol vendor, finds Gugu and takes him in, performing operations to save his life. The accident leaves Gugu's face severely disfigured, and he begins wearing a mask to hide his appearance. People who see his uncovered face call him a monster, which deepens his feelings of isolation and insecurity.

Living and working at Booze Man's liquor store, Gugu eventually meets the immortal being Fushi, who arrives with an elderly woman named Pioran. Recognizing that they are both considered monsters by others, Gugu decides they should be friends and comes to view Fushi as a younger brother. Initially, Gugu feels jealous when Rean shows romantic interest in Fushi rather than in him, but over time the three form a close and supportive group. Rean later moves into Booze Man's shop to treat a wound on her arm, and the bonds between them grow stronger.

Gugu's personality is defined by a complex mixture of insecurity and deep caring. He is warm-hearted and willing to risk his own life for the sake of others, yet he struggles with feelings of self-doubt because of his changed appearance. When the topic of his mask comes up, he becomes defensive and frightened of people trying to see his face, believing his scars would cause others to run away. Despite a somewhat jaded and pessimistic view on life that stems from his poor upbringing and his brother's betrayal, Gugu possesses a caring side and demonstrates remarkable resilience. Over time, with the support of Fushi, Rean, and Booze Man, he overcomes his emotional scars and becomes more confident.

Booze Man performs experimental body modification on Gugu, giving him an extra organ that allows him to store alcohol inside his own body. This grants Gugu a rare and powerful ability to unleash flames by igniting the stored alcohol, effectively using himself as a flamethrower. He combines this firepower with his physically imposing build, which he develops through years of training, making him a formidable defender. His fire-based attacks prove particularly effective against the monstrous Nokkers, who are vulnerable to flames. After his death, Fushi can borrow Gugu's form and fire abilities during battles, a testament to the profound connection they share.

The relationship between Gugu and his biological brother Shin is marked by betrayal and lingering pain. Shin abandons Gugu, taking all their shared savings and leaving him to fend for himself. When they later meet again in an alleyway where Shin lies beaten and destitute, Gugu gives him Rean's valuable ring to help him live a better life, yet when Shin asks if he is indeed Gugu, he responds that he has no brother. Years later, Shin seeks him out again, expressing regret and a desire to reunite as family, but Gugu remains deeply hurt and wary of allowing his brother to take away any more of his precious treasures, referring to the people he has come to love. In contrast, his relationship with Booze Man is one of gratitude and familial care, with Booze Man acting as a protector, mentor, and surrogate father who guides him through hardship and recovery. His bond with Rean deepens from childhood admiration into genuine romantic love, and despite the difficulties posed by their different social stations, he consistently places her safety above his own.

Gugu's development follows a trajectory from a struggling, insecure young man to a confident and capable protector. After a period of running away from Booze Man's shop when he discovers the truth about his body modification, he comes to accept himself with the help of Rean and Fushi. He decides to train his body to make his physical strength his defining feature, transforming himself into a muscular and powerful young man. His acceptance of his circumstances and his identity as someone who can protect others marks a turning point in his personal growth.

Gugu meets his end on Rean's sixteenth birthday, when Nokkers attack the mansion where her birthday party is being held. Despite fighting bravely alongside Fushi to protect Rean and the other guests, he is mortally wounded while shielding Rean from falling debris. In his final moments, Rean opens his mask and kisses him, and he tells her that he loves her. After his death, Gugu's spirit remains connected to Fushi, continuing to offer support and encouragement from beyond. During the war against the Nokkers in the royal city of Renril, Fushi revives Gugu, allowing him to participate in the battle and live peacefully afterward watching over Fushi. During an anti-Fushi uprising, Gugu is badly wounded and chooses a peaceful death with medicine provided by Booze Man. In the modern era, Gugu is resurrected again and becomes a student, demonstrating the enduring impact of his character and the many lives he has touched.