In terms of usefulness and cost compared to the Caravel, the Fune are weaker, causing less damage per cannonball and also have 2 less range. However, they have two advantages, concerning their sailing speed and Rate of Fire, as they boast a slight advantage of 9.0 speed rather than 8.5, while they fire once per second, making them excellent for naval hit-and-run operations, by shelling land positions, or attacking Fishing Boats. They are also ideal (in small groups) for exploiting naval treasures.
In 1281, when the Mongol Hordes of Kublai Khan invaded Japan, the Japanese had no navy with which to fight back. Most of the military action occurred on land, although groups of adventurous samurai utilized coastal fishing boats to assault, board, and then seize ships of the Mongol navy.