Kotarou

Kotarou (公太郎) is an ordinary hamster that obeys orders from a female telepath from Ninoudefuzoku Middle School.

Daihasei Festival Arc (Railgun)
During the three-legged race, he attempts to ambush Amime under instruction by one of the Ninoudefuzoku participants, a telepath whose ability is limited to only rodents, but Amime swats him aside, angering his instructor.

Trivia

 * Kotarou is the only named hamster during the three-legged race. Including him, at least six hamsters were involved in the race.