留美

Youngest of the three sisters, Rumi is not as proficient of a mahjong player as her older sisters, Yumika and Miyabi. She is eager to learn though and vows to someday best them both as well as the protagonist. She wishes for a husband who will let her go shopping anytime she wants, but she knows she's not quite old enough for marriage yet, despite her father's opinion.

She is kidnapped in a plot to undermine her family's near monopoly on mahjong gaming halls. But once she discovers who her captor is, she agrees to play along.