Seiga Kaku is a recurring character in the Touhou Project series, first appearing as the Stage 4 Boss in 'Ten Desires.' She is a wicked hermit known for her mischievous and cunning nature, often manipulating others for her own amusement or benefit. Seiga possesses the unique ability to pass through walls and is recognized for her blue hair and Chinese-inspired attire. In the series, she plays the role of an antagonist and mentor, guiding others toward immortality through Taoist teachings.