Masumi Katagihara (樫原 真澄) is the first daughter and second child of Narumi Ioroi and his wife Tamami Ioroi. She married into the Katagihara House, one of the Sanka (which means subordinate for the houses) houses of Ioroi House. Her husband Seishirou is the next head of Katagihara House.
Unlike her most siblings, Masumi resembles her mother with curly black bob hair that has small tails at two sides.
Masumi is first mentioned by Narumi as already "married out", when her siblings and parents are hanging out.
Later on, she appears in her younger sister Shizuru Ioroi's flashback, where their father Narumi is severely injured. Masumi and her mother are shown worried and sad.
Masumi and her husband had been seen watching the Hadarae Castle Games, alongside her family.
Shizuru later stated Masumi and her husband have recently welcomed a son.
- The name Masumi means "real, genuine" (真) (ma) and "clear, pure" (澄) (sumi).
- Masumi's surname Katagihara means "evergreen oak, (kokuji)" (樫) (katagi) and "field, plain" (原) (hara).