When he was first introduced, Rantaro seemed like a mysterious individual. Later it could be seen that he is a carefree and relaxed person. Despite his mysteriousness, he is described as one of the more ordinary students, with he himself stating that he can sometimes get a bit overwhelmed by the others' stranger personalities. He often talks and acts like he knows something the others don't know, saying profound-sounding and enigmatic sentences, which often make him sound suspicious or eerie.