Akuma Island

Akuma Island is a remote island off the coast of the hi-tech city San Fransokyo in the animated film Big Hero 6 and the base of the supervillain Yokai. The island is now abandoned, but it was once the testing facility for Alistair Krei's teleportation technology. It's failure resulted in the forced shutdown of the project and the desertion of the island.

Geography
The island is nearby the bridge of San Fransokyo and a few miles away from the city. Its surface consists of various plants and rock formations. Despite the evacuation of humans from the area, the island is still teeming with life. A large portion of the island contains the laboratory of the now defunct Silent Sparrow project. The interior of the facility is a large test chamber for the portal. An observation deck adjacent to the portals is within the room where the tests can be monitored and controlled. Due to years of abandonment and wreckage, the facility is now worn down and dilapidated compared to its former pristine state. However, several parts of the equipment are still functional in providing remnants of the facility's past.

Role in the film
Before the events of the film took place, Akuma Island was once the location for a secret test facility owned by Alistair Krei dedicated to the sole purpose of teleportation experiments. This experiment, dubbed Silent Sparrow, involved two portals to transport one object through the other end. However, during the first test with the pilot Abigail, an irregularity that was ignored by Krei caused the re-entry portal to go haywire and suck everything into it. The portal was stopped, but Abigail was lost inside the portal's dimensions and presumed dead. The incident also resulted in the closure of Krei's facility.

Abigail's father, Robert Callaghan, would become murderously enraged by his daughter's supposed death and decided to extract vengeance against Krei for effectively causing this. Under the guise of Yokai, Callaghan returns to Akuma island in present day to retrieve parts of the broken portal to recreate it on the main land with the aid of Microbots.

In hopes of capturing Yokai, the new superhero team Big Hero 6 head over to the island and enter the facility, where they find a recording that reveals the testing history and fate of the facility. Just then, Yokai finds the team and attacks. A battle ensues in the facility, resulting in massive damage as the members try to disable the masked man. After many failed attempts, Yokai's true identity is revealed and he is forced to retreat. While the team's leader Hiro abandons his teammates on the island in a fit of rage, team member Fred is able to call his family butler to rescue them on the family's helicopter. Before departing, the team takes the rest of the footage to investigate the connection between Yokai and the island.

Trivia

 * Akuma (悪魔) means "demon" or "devil" in Japanese.
 * The island is the San Fransokyo version of Angel Island.
 * The Silent Sparrow alludes to the sparrow of Japanese folklore, where the sparrow is said to be a symbol of unexpected fortune and a reward for kindness.