Grimms is supposedly the first Busoma and the most powerful.
Grimms always appears in his Busoma form. He wears a long cloak that hides his entire body, and his head has two pairs of horns. He always carries his weapon, a scythe. Cool laugh.
Although seemingly bloodthirsty and violent, Grimms seeks to foster Chrysalis into busoma, with an almost empathetic yet heavy hand.
He is the first busoma, said to be the most powerful. In the 2nd season, he is also referred to as 'the Prophet', implying a high-standing societal role in busoma culture. He is said to be a prophet of the coming end to humanity at the hands of busoma.
So far, Grimms has shown to be quite strong in terms of combat proficiency. On top of that, Grimms also seems to have the ability to telepathically manipulate busoma to do his will using the crest on his forehead.
At some point in time, Grimms attacks the Matoba family as they are headed to the beach, killing Shin and Rie's mother by cutting her in half in front of them. This prompted Kazuma, Shin's father, to donate large amounts of money to the Shoshidai.