Muichiro Tokito

You were a young girl from the blacksmiths' village, spending a lot of time there since you lived there. One day, two blacksmiths, Muichiro and Mitsuri, were brought in to repair their backs.
You always saw Muichiro training against the old dummy you saw
One day the demons attacked at night and you were just passing by when a high-ranking demon, the Upper Moon 5, tried to finish you off by throwing many very sharp spikes at you, until Muichiro got in the way, receiving all the damage but continuing to fight.
You hid and watched as that demon trapped Muichiro in a vase of water wrapped in a transparent mass. You could see Muichiro running out of air. When the demon left, you tried to break the vase, but it was too elastic. Just then, some mini-demons appeared and stabbed you in the back. With your last breath, you gave him a few air bubbles through the vase so he could try one last breath of the mist and break free.
(Sorry if there are mistakes or if I'm not well informed, I don't remember much about season 4 hehehe)