Nyubachibo - 乳鉢坊 - [yokai] - 'mortar-monk'
• About this Yokai: a Tsukumogami of an antiquated mini gong (called a "Nyōbachi") played & commonly used in both prayer & during theatrical performances. (Nenbutsu dances, etc.) it surprises people and rings with a noise so sharp, that it might wake up the gods themselves...
• History: Another yokai by Toriyama Sekien included in his "Horde of Haunted Housewears." - Despite it resembling a Chinese gong (Called a "Nyōbachi" ) Sekien instead named it "Nyubachi" meaning "Mortar" (as in mortar & pestle, the kind used for grinding herbs & medicine.) - its a simple play on words, the two the objects resemble each other. (& both are “instruments” to drive away plague and illness.) - "bo" is short for “bozu” or "monk" (he’s dressed in monks robes) - continuing with that theme, in the same illustration, along the bottom is "Hyotankozo." ["Gourd boy."] - Gourds were valued as containers and were often used to store alcohol and medicines. According to some, spirits were believed to dwell within gourds.) the banner behind them depicts Buddhist imagery such as the lotus and manji.
[background image is the original by toriyama sekien, edo period 1784 - Sekiens included prose translates close to as follows: "Shocked green at the sight of gourd boy, mortar monk clashed his cymbals together loud enough to wake me from my dream." - via “japandemonium”] given that nenbutsu dances and the like are an obon custom (for the dead) it makes some sense that the nyubachibo perhaps got surprised seeing the sickly looking gourdboy and began ringing to wake him up! - thus, its often said to be a yokai that wakes people up or causes a ruckus, startling them awake with sudden loud noises!
...Also quite often mentioned in writings about these two is the similar 'cymbal/gong' tsukumogami which is depicted in earlier Muromachi period (1333-1573) - "Hyakki Yagyo Emaki" picture scrolls, which Sekien referenced in his preface as inspiration for certain yokai (such as Waniguchi.)
however, it’s worth note that that is just a theory. The depicted yokai has a long nose (similar to a tengu) & appears to be singing a chant along with others in that part of the parade. I’ve seen the one behind him called a cat or a nekomata too… so it could have been something else entirely (notably this scroll lacks any names or proper context for whats going on, so it's difficult to say for certain if they're truly the same. Theories are fun though! 🤷 regardless, I suppose it shows that this sort of instrument monster has existed for a very long time.)
This tsukumogami was re-drawn by Yoshitoshi and appears along side several others in color In his Night parade of 100 demonic objects 
see also: Tsukumogami, waniguchi, Shogoro
PS: if you like my take on this yokai you’ll definitely love my friend nanas adorable yokai comics ❤️😝