Rintarō Shinjuku personifies Shinjuku Station, designated E27 on the Toei Ōedo Line. He has dusty brown hair and distinctive purple eyes, contributing to a model-like appearance that complements his flirtatious and occasionally narcissistic personality. This demeanor includes a noticeable preference for assisting female passengers, shown by his initial reluctance to help the male passenger Keita Sakuraba before ultimately joining the other stations to resolve Keita's issue.

Within the Miracle Train group of station personifications, he maintains relationships built on mutual support despite occasional disagreements. His interactions, such as those with the serious leader Tochō Saki and the younger Shiodome Iku, highlight both his playful tendencies and an underlying sense of team responsibility. He is mentioned to have three brothers.

His role involves engaging with passengers boarding the Miracle Train, frequently using his charm to address their emotional struggles. In Episode 3, he encountered the passenger Michi, who initially hated trains due to her parents' obsession; his intervention helped shift her perspective. His character remains focused on aiding others within the episodic structure, without significant personal development or expanded backstory. He appears exclusively in the original 13-episode anime series.