Li Gado

Li Gado is an intelligent microbe and a hyperdoctor specialized in fighting pathogens using weaponry. He wears an exosuit similar to a flea that shields him from the atmosphere, and operates a small round robot to work.

Li Gado came to Hellsalem's Lot in pursuit of the terrorist pathogen Gemnemo to capture him, but the weapon he constructed to do it got destroyed when it collided with Leo’s head. He follows Leo home to build a new weapon, and uses the occasion to tell him about Gemnemo’s threat and the danger of not stopping him, but Leo has a hard time taking the Gemnemo threat seriously. Using the undamaged parts from the original weapon Li Gado constructs a new one, but since he can’t use it because his regular gear is under repair, he recruits Leo to aid him after seeing him use his eyes to guide Sonic.

(Source: Blood Blockade Battlefront - Kekkai Sensen Wiki)