|Romanized Name||Arisugawa Masaomi|
|Relative(s)||Houko Arisugawa (Mother)|
Reiko Arisugawa (Younger Sister)
Masaomi Arisugawa (有栖川正臣 Arisugawa Masaomi ) is the elder brother to Reiko, and a supporting character in the series.
Masaomi is young handsome man who resembles his father, and he is also very tall. He has black, chin-length hair and brown-blue eyes.
Masaomi is a very gentle brother, and Reiko described him to be very caring and kind, and he visits her very often. He appears a little overly concerned, but he is caring and kind one in any case. However, if it means harm och to hurt Reiko, he can be a little cold, like to Kimito.
Masaomi is present when his mother announces that has sister marriage partner has been decided.