The follow up conversation has been moved here:
https://www.axisandallies.org/forums/topic/36451/submarine-movement-and-customized-map
When an aircraft leaves a coastal territory or island, does it cost one point to move into the sea zone adjacent to the territory/island? for example, If a plane leaves Japan on the pacific map, does it cost one movement point to move in to sea zone 6? The way I read the rules, it does.
Yes, it does cost a movement point.