Whisper is a ghost-like yo-kai liberated by Keita after 190 years of imprisonment. This act prompts Whisper's pledge of loyalty and protection against supernatural threats, establishing a dedicated guardian role. He provides Keita a special watch enabling visibility and interaction with other yo-kai.

Physically resembling an ethereal, spectral figure whose features suggest an ice cream cone, Whisper embodies a comedic yet earnest persona. Though nominally serving as a butler, his efforts often backfire comically despite genuine intentions. He primarily guides Keita through encounters with various yo-kai causing everyday disturbances, maintaining a dynamic partnership with the fiery twin-tailed cat spirit, Jibanyan.

Within the anthology "Enma Daioh to Itsutsu no Monogatari da Nyan!", Whisper appears across interconnected segments. These include observing Keita's transformation into a yo-kai following an encounter with Enma, and participating in the ensemble finale addressing Enma's illness and a ban on human-yo-kai contact. Throughout these events, Whisper provides continuity and minor support while the narrative focus remains on other characters like Jibanyan or Inaho.