Rumia is a youkai from the Touhou Project series, specifically appearing as a stage 1 boss in the game 'Touhou Koumakyou: The Embodiment of Scarlet Devil.' She is known for her ability to manipulate darkness, creating an aura of mystery and danger around her. Despite her menacing power, Rumia is portrayed as a relatively carefree and somewhat naive character, often flying around aimlessly. Her role in the series is to challenge the protagonist as part of the game's early stages, testing the player's skills before encountering more formidable foes.