Doku is an elderly resident of Manoyama who serves as a connective link to the town's vibrant and tumultuous past. His background is rooted in the counterculture of fifty years prior to the main events of the story, when he was a young man with ambitions that stretched far beyond the shrinking confines of his rural home. During that time, he was a member of a rock band, a trio that included his friend Kadota and a young woman named Chitose, who would later become the grandmother of Ririko Oribe. This group shared a powerful dream of escaping the stagnation of Manoyama and moving to Tokyo to pursue their musical aspirations.

In the present day, Doku's personality is largely defined by his role as a chronicler of this forgotten history. He is a person who has made peace with the past and carries its memories with a sense of clear-eyed reflection. While the specific details of his daily disposition are not extensively detailed, his function in the narrative is to provide context and understanding, helping to bridge the generational divide that exists in Manoyama. He does not harbor the same bitterness or regret that characterizes some of his old friends, instead presenting the events of the past with a straightforward and almost fond matter-of-factness. He is the one who finally reveals the full story of what happened to the town's festival fifty years ago, explaining the deep-seated rift between Kadota and Chitose that had persisted for decades.

Doku's primary motivation, as demonstrated through his actions, is a desire for truth and resolution. He holds the key to understanding why Manoyama lost one of its key cultural events and why its people became so fractured. By sharing his memories, he enables the younger generation, specifically the members of the tourism board, to grasp the root of the town's decline and take meaningful steps towards its revival. His role in the story is therefore crucial; he acts as a catalyst for the main characters, providing them with the historical knowledge necessary to solve a long-standing mystery involving the disappearance of relics in a local pond and inspiring them to attempt a revival of the lost festival.

His most significant relationships are with his former bandmates. His friendship with Kadota and Chitose is the core of his history, and his recollections define how the town understands these two elderly, influential figures. While he was a part of their shared dream to leave, he was not the one who betrayed it. Instead, he serves as a neutral party whose testimony clarifies the actions of the other two. This revelation, particularly for Ririko, fosters a new sense of understanding between her and her grandmother, Chitose, showing how the disappointments of the elderly have shaped their protectiveness over the young.

In terms of development, Doku remains a static character, but his function is to enable the development of others. His decision to come forward with his story represents a willingness to close a painful chapter of the town's history, allowing for healing and progress. His notable ability is not a physical or professional skill, but rather his reliable memory and his capacity as a storyteller. He possesses the firsthand knowledge of Manoyama's more spirited and hopeful youth, as well as the musical talent that was a part of that era. His flashback reveals the rawness and freshness of the band's sound, which was ahead of its time, featuring both a male and female vocalist in a rock context. This ability to recall and articulate the past with accuracy and without malice makes him an invaluable, if quiet, force for change in Manoyama.