Arthur Buttmann is the younger of the two Buttman brothers, growing up with his older sibling Abel and their adopted sister Georgie on a farm in rural Australia during the latter half of the 19th century. He and Abel are biological siblings, while Georgie is a foundling brought into the family by their father. From a young age, Arthur develops deep romantic feelings for Georgie, a secret he carries into adolescence and adulthood.

In terms of personality, Arthur is consistently portrayed as kind, selfless, and empathetic. Unlike his more impulsive and passionate older brother Abel, Arthur is the sensitive and rational counterpart who prioritizes Georgie's happiness and well-being above his own desires. He frequently acts as a mediator, attempting to cover for his mother's cruel treatment of Georgie and trying to prevent Abel from revealing the truth about their family's secret in a way that would hurt her. Arthur refrains from forcing his affections on Georgie and is willing to step aside for her happiness, demonstrating a level of emotional maturity and restraint that distinguishes him from his brother.

Arthur's primary motivation throughout the story is to protect Georgie and preserve the harmony of their family unit. When Georgie is cast out of the house by their mother Mary after the revelation that she is not a biological daughter, it is Arthur who saves her from drowning in a river. In a notable and controversial scene, he uses his own body heat to warm her when she suffers from severe cold exposure. After Georgie decides to travel to England to find her biological parents and her love Lowell Gray, Arthur initially attempts to stop Abel from following her, believing she should be free to pursue her own path. Following the death of their mother from grief, Arthur eventually journeys to England as well.

In the English arc of the story, Arthur's role becomes more prominent as he uncovers dangerous secrets. He is taken prisoner by the Duke Dangering, a powerful noble who had framed Georgie's biological father for a crime. During his captivity, Arthur endures significant hardship, but he remains loyal to Georgie and refuses to compromise his principles. His imprisonment ultimately becomes the catalyst for the final resolution of the plot, as Georgie, Abel, and her biological father work together to rescue him and expose the Duke's conspiracy.

Key relationships define Arthur's character arc. His bond with Georgie is one of unrequited devotion; he loves her deeply but rarely acts on his feelings, choosing instead to support her from the sidelines. His relationship with Abel is complex, marked by both brotherly loyalty and rivalry over Georgie's affections, though Arthur consistently defers to his older brother while trying to temper Abel's more reckless impulses. Arthur also attracts the unwanted attention of Irwin Dangering, the Duke's son, who holds him prisoner. Additionally, Maria Dangering, Irwin's sister, develops genuine feelings for Arthur and ultimately aids in his escape.

Throughout the series, Arthur undergoes notable development. He begins as the quiet, supportive younger brother who suppresses his own emotions for the sake of family peace. As the story progresses, he becomes more proactive, traveling to England and confronting the dangers of the aristocratic world to protect those he loves. His imprisonment and the subsequent rescue attempt test his resilience, but he emerges with his compassionate nature intact. In the anime's conclusion, Arthur returns to Australia alongside Georgie and Abel, choosing to leave behind the turmoil of England and return to the simpler life of their youth.

While Arthur does not possess any extraordinary abilities, he is portrayed as physically capable, resourceful in dangerous situations, and emotionally intelligent. His strength lies not in combat or cunning but in his unwavering kindness and his ability to endure personal suffering for the sake of others' happiness.