In Hand (2019)

Himokura Tetsu is a scientist who specialises in the study of parasites. He loathes people and is very sadistic. Tetsu bought a huge botanical garden in Hakone which he converted into his home and lab. He holes up in the conservatory where he researches his favourite parasites. His right arm is fitted with a black robotic hand. However, it is not known how this artificial hand came about. He is an eccentric genius who solves a series of difficult cases with astounding scientific methods.