Rui was a quasi-calm, aloof and somewhat polite individual, rarely raising his voice, and talking with everyone, demon or Demon Slayer, with a reasonable tone and vocabulary, though his low and guttural way of speaking seems to imply repressed anger and annoyance. Despite this stark difference in demeanor when compared to most demons, Rui was actually a disturbed individual who desired the close bonds that a family had and expected family members to perform their own roles.