Fumi Roppongi personifies Roppongi Station, designated E23 on Tokyo's Toei Ōedo Line. He has brown hair extending to his neck and blue eyes. Calm, kind, and mature in demeanor, he often appears reserved yet observant, detecting unspoken troubles in passengers as shown in early cases. He habitually reassures others with the phrase "Don't worry."

Highly proficient with computers, he meticulously documents passenger interactions and assistance outcomes in reports. Ten years before the main storyline, he encountered a young girl named Akari during her school trip after she became separated. Discovering him collapsed near the train, she helped him board the Miracle Train, inadvertently binding herself to it as a tour guide. This incident created an operational abnormality requiring Akari’s return to her original timeline to live normally. As an adult, she reunites with him, retaining memories of their shared past; mutual romantic feelings are implied.

Within the Miracle Train group, he maintains positive ties with fellow station personifications and Tokugawa, their pet dog. He collaborates effectively during missions, such as aiding a runaway girl’s search for her missing father. Roppongi Station itself, located in Minato, Tokyo, holds Japan’s deepest station distinction at 42.3 meters underground. Jointly operated by Tokyo Metro and Toei Subway, its Hibiya Line station opened on March 25, 1964, and the Ōedo Line station on December 12, 2000.