付喪神 - Household items that have come to life
An everyday item or tool that has become a Yokai. It is thought they gain a spirit after one hundred years2, and thus a degree of sapience. Most are benign—either guardians or tricksters, though a few will harm humans. These spirits may be angry at being thrown out by their human masters, while others may protect members of the household. It depends on how the previous owners or how those who discover the spirit treat it. With care, some malevolent spirits can be appeased.
A kosode (short sleeved under kimono) yokai
Kosodenote by Ryūkansai
Kasaobake, an umbrella spirit
Kasaobake by Jinbunsha? (Public Domain)
Tofu Kozo- spirit boy carrying tofu and sometimes sake
Tofu Kozo by Ryuukansaijin
Chou an ooze, thought to have originated from a forgotten batch of agar1.
Liminal Chronicles Series bookcover art by Odette.A.Bach. Book and short story bookcovers by Amy Winters-Voss with Flaticon.com icons
1. Areas the author has deviated from traditional ideas.
Fun Kanji Notes:2. It might also be written with different kanji (九十九神 - 99 kami (gods) or 九十九髪 - hair of 99 (years of age)). This may be where the 100 years aspect comes into play.
Dr Emily Vair-Turnbull
That picture of the Chou is the most adorable thing. :D There's so much potential for different ideas here.