Despite the name Sevii Islands, there are nine islands (Seven initially accessible, two accessible by promotion).
The name "Sevii" is a corruption of the English word for Seven, containing the Roman Numeral "VII" as a suffix. It was named the Sevii islands because it was believed to have been created in seven days.
Tri Pass allows the player to visit islands 1, 2 and 3.
Rainbow Pass allows the player to visit islands 1, 2, 3, 4, 5, 6 and 7.
Special Tickets (obtainable through promotions) allow the player to visit the remaining two islands as defined by the ticket.