Higemaru Makaijima (or Higemaru Makaijima: Nanatsu no Shima Daibouken to give it its full title, which translates to something like Higemaru Hell Island: Big Adventure of 7 Islands) takes the basic concept of Pirate Ship Higemaru, the Arcade game on which it is based, and expands on it, creating an adventure game as expansive and in-depth as the Legend of Zelda.
The goal is to sail around until the player finds a pirate ship (the friendly green merchant ships will simply provide hints) and clear the boss. Doing so will allow the player to collect a port key which allows them to set anchor on one of the titular seven islands. The player must then remove the boss of that island and recover the treasure. At which point, the process must be repeated.
This notes the first game that Capcom created a brand new game for the Famicom console (though it's worth noting that this game was available for the MSX home computer as well). The previous five Famicom games from Capcom were simply ports of their previous Arcade games.
The gameplay is more or less identical to that of Pirate Ship Higemaru, as the sailor protagonist Momotaro must pick up barrels (and later rocks) and throw them at enemy pirates that swarm the stage. Hitting pirates will replenish Momotaro's health, which is indicated by a number in the top left of the screen. Bonuses can be earned if the player takes down many pirates with a single barrel throw, similar to Pac-Man's scoring system.
The non-action parts of the game require that the player sail around the world map visiting islands they have access to and tracking other ships on the sea.