|1||0||Exchange HP and MP levels.|
HP↔MP swaps the character's HP with their MP. This allows the character to boost their MP above 999, which is the typical reason HP↔MP is used. However, it will also cap a character's HP at 999, making them extremely vulnerable. To work around this, high Defense, Defense%, Magic def, and Magic def% are highly recommended, along with defensive abilities such as Counter.
HP↔MP can be used for Limit grinding, as the user's Limit gauge fills faster when the enemy's attack takes more of their max HP, and with such high MP they can clear waves of enemies with group-cast Magic and E.Skills. It can also be used for general level grinding sessions as to have a reservoir of MP that lasts a long time, as long as the user can survive with such low HP.
HP↔MP can also be used to trigger the All Lucky 7s status since manipulating a user's MP to 7777 may be easier than manipulating their HP, as the player can carefully select their MP cost from the abilities they have to achieve it, and then remove the HP↔MP to end up with 7777 HP and All Lucky 7s.