Masumi Kamuro is a student of Class 1-A and a member of the Art Club. She is usually seen together with Arisu Sakayanagi. Masumi is a very honest and loyal girl who hasn't done any damage to the interests of the class. She is close with Arisu Sakayanagi, and willingly follows her orders. She is known to be a shoplifter. Masumi was first seen walking with Arisu Sakayanagi in the school's back alley while holding an umbrella for her. Later, on the school cruise ship she was seen at the 4-star restaurant, along with several other students who are presumably from Class 1-A, as they were staring at one of the students from Class 1-D, who grabbed another student from A-class, who started mocking them because of being in the lower class. She was also the one on the phone with Arisu, as the latter was seen to be setting the school trip out, due to her illness, playing chess at the library. Arisu then asked Masumi to investigate some students for her.