Chiranosuke is a spirit entity who serves as a guide and advisor to the protagonist, Yuta Iridatsu, throughout the events of Punch Line. He is a small, white-furred cat with lemon-colored eyes and a blue, ethereal tail that marks him as a ghostly being. Unlike an ordinary cat, Chiranosuke rarely walks on all fours; he is most often seen floating in the air, either resting on his back or side or hovering upright in a human-like posture.

His name is a pun that reveals much about his personality, combining the Japanese words for a glimpse or peek, chira, with a shortening of sukebe, a term for a lecherous person. True to this namesake, Chiranosuke has a pronounced and often comedic fixation on inappropriate topics. He has a habit of explaining complex spiritual rules and abilities using analogies involving breasts and frequently uses his computer to look up irrelevant or perverse material, such as videos of cats mating, which leads Yuta to accuse him of doing it on purpose. This lecherous and eccentric demeanor, however, belies his true nature as a being of immense experience and a key player in a grand, long-running struggle.

Chiranosuke's primary role is that of an exposition fairy and spirit advisor, tasked with helping Yuta navigate his predicament as a disembodied spirit. He explains the rules of Yuta's out-of-body state, including the bizarre and crucial consequence that seeing a girl's underwear twice in a row will cause an asteroid to destroy the Earth. He instructs Yuta on how to use poltergeist powers and guides him in his search for a mystical book called the Nandara Gandara, which is necessary for him to return to his physical body. Chiranosuke is a member of the Human Preservation Project, an organization dedicated to preventing the asteroid impact that would cause human extinction. To this end, he has worked through an astronomical number of iterations. He reveals that he has been with over six billion versions of Yuta so far, each one attempting to break the time loop that dooms the planet. Chiranosuke himself originates from a single, happy, and peaceful future where one version of Yuta succeeded, and he has since been traveling through the loops to ensure that success becomes the final reality.

Key relationships define Chiranosuke's function in the story. His most significant bond is with Yuta, whom he constantly advises, teases, and pushes toward the goal of saving the world. He serves as the primary source of information for the protagonist, however crude that information might sometimes be. Furthermore, the visual novel adaptation expands on his background, revealing that Chiranosuke had also been secretly possessing Yuta's sister, Akina Iridatsu. He did this to covertly influence events and ensure Yuta would be set on the right path to break the cycle of destruction. His connection to the physical world is also touched upon in the epilogue, where it is shown that the NEET resident Ito Hikiotani begins caring for a pet cat named Chiranosuke, though this seems to be a separate, living creature from the spirit entity.

In terms of development, Chiranosuke is a static character in terms of personality, but his backstory provides a profound sense of scale and purpose. He is not merely a perverted comic relief character; his lecherous habits mask the weariness of an entity who has witnessed the same failure play out billions of times. His true motivation is singular and unwavering: to finally end the loop and save humanity. His notable abilities include his spiritual nature, which allows him to float, remain unseen by most ordinary people, and possess the bodies of humans like Akina to guide them from within. He also possesses a deep, encyclopedic knowledge of the time loop, the rules governing spirits, and the future events that must be changed.