relating to the nature of azakana and how they form, yasuo and yone were both preyed upon by type’s of azakana that are discussed in the aforementioned post. in the cinematic, kin of the stained blade, the azakana that had been haunting yasuo and was sealed by yone in the end became the mask for an azakana of petty jealousy.
knowing this, it is reasonable to infer that the azakana who hunted yone in life was an azakana of obsession turned to malice. this can be assumed because the brothers are used to represent the legend of the two brothers who were split by the same forces in the path. it should be noted that spirit blossom yasuo and spirit blossom yone are not really yasuo and yone; they are more like actors dressed up as other people, those being the two brothers from the legend.
the collector had grown jealous of how many spirits the gatekeeper had lead to the afterlife, so he took two of his loudest bells, and melted them down and hammered them into blades over twelve nights. into one blade, the collector poured some of his jealousy, and into the other, he poured some of his obsession. in spring, he let the spirits of the swords bloom into the physical realm, and they grew from the ground like saplings.
the path shows the older brother fighting a demon of obsession, and because yasuo and yone’s actual stories / lore are meant to be similar to the legend, it is reasonable to infer yone’s azakana was an azakana of obsession turned to malice. however, things do become slightly fuzzy towards the end of the path’s cinematic considering we saw the elder brother defeat the azakana, and then the setting suddenly shifts into present day, were we get a glimpse of the real yone. it is possible that other swordsmen had defeated their azakana as well, or perhaps the elder brother’s azakana took him with him / possessed his body. it is unclear and the answer remains unknown as at present time, yone is the only swordsmen to have fought his azakana, defeated it, and then returned to the physical realm. he does not know how or why, and ultimately still does not know the name of the azakana who has hunted him in life.