Here is a description of Suisen, via our previous coverage:
A boy with a mechanical body, he is the “Clairvoyant Magistrate,” one of the “13 Magistrates” of the Shogunate. He stands in the way of Fuji and company, who are on a journey to overthrow the Shogunate.
While he may look young, he is a self-aware biological weapon with high combat power. With his high information processing power, he fights by predicting the future based on gathered information.
He usually speaks in a plain, robotic tone, but sometimes speaks as childishly as he looks.
Watch the trailer below.