The manga serves as a continuation of the Meiji Jūzoku Tungsten series, set during a period of rapid change in Japanese history. The story takes place in Taisho 7 (1918), a brief era of economic prosperity following World War I.

The central character is Ryoji Saeki, a planning engineer in his mid-thirties who was educated in Europe. He travels across Japan with his lover and invaluable work partner, a foreign man named Edward, dedicating himself to the expansion of the nation's electrical power infrastructure. Their current, relatively peaceful life is interrupted by the arrival of a letter from Kaoru Nakahara, Ryoji's former benefactor and a figure of great significance from his past.

This letter triggers a narrative that unfolds along two timelines. The first is a flashback to Ryoji's youth, depicting his initial meeting with Nakahara, the circumstances under which Nakahara took him in, and how the older man provided him with an education and a path forward in life. These scenes explore the complex and ambiguous nature of their relationship, revealing the profound debt and complicated emotions Ryoji carries. The past storyline also delves into Nakahara's own life, including his marriage, and the personal struggles that led him to reach out to Ryoji once again.

Concurrently, the narrative returns to the Taisho 7 present to explore Edward's backstory. The arrival of Nakahara's letter sets in motion events that lead to revelations concerning Edward's own family and his origins, connecting his past to the network of people surrounding Ryoji. The volume thus weaves together the story of a younger Ryoji and his mentor with the current-day mystery surrounding Edward's relatives, ultimately bringing long-buried truths to light for both protagonists. The work is a period drama that uses the backdrop of Japan's technological modernization to frame a story of personal debts, the formation of identity, and the enduring bonds between its main characters.