Movie
Description
Suiko Tatsunagi is the eldest sister of the Tatsunagi siblings, Rekka and Kourin. She helps manage the card shop PSY and is a member of the pop idol group Team Ultra-Rare. At PSY, she sets pivotal moments in motion, presenting Aichi Sendou with the King of Knights, Alfred card and later offering him a critical choice between two powerful cards representing light and darkness; Aichi's hesitation over this choice indirectly leads to the emergence of Majesty Lord Blaster.

She possesses cyan hair and violet or blue eyes. Suiko typically wears a blue sweater with a yellow scarf during her early appearances before enrolling at Fukuhara High School, where she dons the school uniform. For Team Ultra-Rare activities, she wears the group's distinctive idol outfit.

Suiko generally maintains a calm, settled demeanor, acting as a discreet facilitator who skillfully conceals her intentions. However, she flares with intensity when provoked, such as reacting fiercely to Naoki Ishida's comment about her sailor uniform appearance. This sparks a competitive rivalry with him, marked by strategic cardfights where she demonstrates proficiency with Perfect Guard tactics; she later acknowledges his growth after their rematches. Her abilities extend beyond typical cardfighting, granting her perception of events on the planets Cray and Brandt.

Her enrollment at Fukuhara High School begins under the directive to monitor powerful cardfighters, particularly Ren Suzugamori. This assignment precedes her becoming a PSYqualia Zombie. In this reversed state, she exhibits sadistic tendencies and spreads the condition to others like Minami Kawanami and Asaka Narumi. After Kouji Ibuki liberates her from this state, her connection to the Vanguard game is severed. Consequently, she adopts a more emotionless disposition yet continues serving the Destiny Conductor, Takuto Tatsunagi. As a Called Walker, she is eventually erased from collective memory.

Her cardfighting involves significant battles and deck transitions. Originally using an Angel Feather deck, she switches to Link Joker after becoming reversed. Key duels include her loss to Ren Suzugamori, who defeats her using Raging Form Dragon, and her subsequent observation of his matches against Asuka and Tetsu.

A manga flashback reveals her indirect role in fracturing the friendship between Ren, Toshiki Kai, and Tetsu by engaging Ren in a cardfight that first triggers his absorption into PSY Qualia's power. Later, within the alternate universe narrative of Cardfight!! Vanguard Gaiden: If, she features as a central character alongside Kouji Ibuki, exploring divergent storylines.

Her surname, Tatsunagi, combines the characters for "standing" (立) and "calm" or "lull" (凪), mirroring her poised but pivotal nature.