This type of netsuke is called Manjyu netsuke. This technique is called a vermilion lacquer finish, in which the Kakudaishi and the back of the sword are painted in vermilion.
Ganzan Daishi (元三大師) Hieizan Tendai-zasu (the top rank of Tendai Buddhism) became a demon during meditation. When he made his students copy that on wood plaques and put them on the door of private houses, an epidemic subsided and the affected people were completely relieved. Because of this, they have been handed down at temples of the Tendai sect as a talisman to protect against evil. I carved the figure and the Kiriku of the Sanskrit character into algae balls, and prayed that the owner would be protected agains an epidemic and fulfill his/her wishes.