To explain Hearth-Guarding Old Nekomata in detail:

The Hearth-Guarding Old Nekomata is a version of a cat that has been kept in one place for many years, growing old by the hearth stained with soot and ash, until one night it suddenly manifests with a tail split in two. Positioned at the opposite extreme from the violent Nekomata that attacks humans in the mountains (as noted in texts like "Meigetsuki"^[1]), this being inhales the breath of the house and its generations of life, absorbing the spirit of fire and cooking smoke, and thus behaves much like a household deity (or Zashiki-warashi). While it is an extension of the folk belief that "a pet cat transforms" cited in "Tsurezuregusa"^[2], it carries a much more protective nature. Even without using human words, it signals by clinking the pot lid or drawing patterns in the ash. The pale ghostly fire (Nekomata fire) that darts in the corner of the parlor late at night is not a curse fire to be feared as in "Yamato Kaiiki"^[3], but is rather considered a purifying mark where this old Nekomata preemptively licks away the house's fire hazards and burns off evil energies. In some villages, it is believed that one tail connects "the lineage of the family" and the other "the divine spirit of fire," making the split not a mere deformity but a sacred sign holding dual duties.

The Old Nekomata always draws near when the family gathers around a corpse. There is a common fear that cats resurrect the dead, often causing confusion with the Kasha (the monster cat depicted snatching corpses in works like "Gazu Hyakki Yagyo"^[4]). However, this version never causes a disturbance; it merely sniffs the ragged breath with its nose and lights a small spark to dispel lingering earthly attachments. Therefore, the proper etiquette is for the family not to brandish blades before the Nekomata, but instead to burn a single stick of incense as a "farewell fire." If a long-kept cat is treated roughly, the stove will burn empty in the dead of night, and overlapping wet footprints will appear on the walls. Conversely, in homes that mourn respectfully, folklore akin to the "urban legends" pointed out by Kunio Yanagita survives: on a snowy morning, only the space under the shoji is warm, and the shadows of mice vanish entirely from the rice bin.

This version is sometimes spoken of as an old cat that once disappeared into the mountains returning out of longing for the house, or as an old indoor cat whose tail split naturally over time. The custom of cutting tails to prevent transformation (the origin of the bent-tail cat) also exists, but in areas protected by the hearth-guard, this is taboo, with strict warnings that "injuring the tail will also split the family's fortunes." In appearance, its back skin droops to look like a cloak, casting a shadow-like figure in dimly lit rooms. This is why it is mistakenly thought to shapeshift into the dead, but the Old Nekomata dislikes unnecessary transformation. When it occasionally borrows the appearance of a grandmother, it is only to lull a child to sleep, making no sound and leaving behind only the scent of soot and ash.

Though it does not show itself to travelers, during milestones of the house—such as taking in a groom or the first night in a newly built home—it taps its claws lightly under the floorboards to foretell fortunes. Three taps mean good luck; two mean beware of fire. If the lamp wick is damp, it smoothes it with its tongue; if the stove fire is too strong, it fans it weaker with its tail. In exchange for taking on these small daily troubles, a custom remains for the family to share the "edges of the meal" with it. Three grains of rice, a pinch of salt, and a little steam. As long as these are observed, the Nekomata will not bewilder humans, and the strange noises at night will be dismissed as mere "house creaks."