Fortune Arterial unfolds on Tamatsu Island, where Kohei Hasekura transfers to a prestigious public school modeled on an English six-year academy that brings junior-high and high school students together far from the mainland. The island can be reached only by boat, and the school’s polished everyday routine conceals an unusual secret. Soon after arriving, Kohei discovers that Sendo Erika, the girl in the class next door, is not an ordinary student but a vampire. What begins as a simple transfer quickly turns into a quiet entanglement with the hidden side of the island and the people who live there.
As Kohei settles into campus life, he is drawn closer to Erika and to other students around her, including Iori Sendou, Shiro Tougi, Kiriha Kuze, and the sisters Kanade Yuuki and Haruna Yuuki. Ordinary classes, friendships, and school traditions continue on the surface, while darker truths remain carefully out of sight. The contrast between everyday school life and Erika’s supernatural nature gives the series its tension, mystery, and uneasy charm, with Kohei gradually rethinking both Tamatsu Island and the people he thought he understood.