Kourin Tatsunagi is a supporting character in Cardfight!! Vanguard: Asia Circuit Hen. She is the middle of the three Tatsunagi sisters, with elder sister Suiko and younger sister Rekka. Together, they operate the card shop PSY and perform as the idol group Team Ultra-Rare. Kourin is also the adoptive sister of Takuto Tatsunagi, the enigmatic boy who sets the events of the Asia Circuit in motion. She is a teenage girl with very long blonde hair and green eyes, and her demeanor is often reserved and distant when dealing with anyone outside her immediate circle. Beneath this cool exterior she holds a quiet fondness for Aichi Sendou, showing subtle signs of attachment and taking opportunities to be near him.

Kourin’s background is tied to the powerful Tatsunagi financial group, which grants her and her sisters a prominent position in the cardfighting community. She assists in running PSY and uses her influence to observe rising fighters. During the Asia Circuit she primarily acts in support of her family’s interests, yet personal feelings sometimes lead her to act independently, such as when she personally presents Aichi with the first-place trophy. After Aichi unwittingly activates Takuto’s virtual card system, Kourin challenges him to a cardfight, ostensibly to test his skills. In battle she relies on a Royal Paladin deck that focuses heavily on Critical Triggers, allowing her to mount swift and aggressive offensives. She proves to be a capable fighter, pushing opponents like Aichi and Toshiki Kai to their limits in their respective matches.

Kourin’s key relationships centre on her sisters, with whom she shares a close bond in both business and performance, and Aichi Sendou, for whom she harbours a one-sided romantic interest. She acts as a link between the elusive Tatsunagi family and the main cast, appearing at important moments to move the story forward. Although her screen time in Asia Circuit Hen is limited, her presence deepens the mystery surrounding Takuto and adds a human element to the otherwise aloof Tatsunagi siblings. Throughout the season she shows little overt personal change, but her interactions with Aichi reveal a gradual softening of her guarded nature, hinting at the deeper connections that later arcs would explore. She remains a composed and graceful figure, balancing her duties as a shopkeeper and performer while quietly supporting the central cardfighters.