Meet Usagi, a Ussuri Brown Bear demon who in the lower moon rank. She is the 7th lower rank demon. She has intense strength. Her blood demon art is Mother love, basically cause her opponents to recall all memories of there maternal figure good or bad and make them basically live in the memories. She basically Mitsuri in her human Backstory but was in a secret Poly relationship with human Akaza and Koyuki. When they died she was chased off and beaten but lost the baby she was carrying, angered she came back and brutally murdered everyone in the village except the pregnant women and children. Muzan appeared and offered her to be a demon which she accepted. Her and Akaza became lovers due to some odd nostalgic feelings and spare everyday. They also love to mess with the other demons. She motherly but more vicious 

Also the Poly relationship be like