Muramasa has dark fur with Kneesock design (the end tips of chin, legs and tail has light fur on it).
First found at the Back Garden of Ousai Academy when Aria was showing Takatoshi the cat ring tone in her mobile, pointing their cats react with it. After bringing him to the Student Council Room, Aria requested Takatoshi to do something about it because her, Shino and Suzu were not able to keep a new pet at home. So, after asking his parents, Takatoshi accepted to adopt the cat. Afterward, it was named by Kotomi.