Hakkekkyuu U-1146

白血球 U-1146番, Neutrophil, White Blood Cell (白血球)
He is a White Blood Cell specifically a Neutrophil working under the Neutrophil Division. Along with the other neutrophil comrades hes tasked to patrol around the Blood Vessel and remove any invading Foreign Substances such as Germs and Viruses. Source: Cells at Work Wikia