Kourin Tatsunagi is the middle child of the Tatsunagi family. She is the older sister of Rekka Tatsunagi and the younger sister of Suiko Tatsunagi. Together, they run a card game shop called "PSY" and form an idol groupe called "Team Ultra-Rare".

In Cardfight!! Vanguard (2018), Kourin is one of the main characters in the show and becomes the co-founder of the Miyaji Academy Cardfight Club. She specializes in using the Gold Paladin clan.