From Aerostar's 'Battle Mechanics Guide', available at gamefaqs.com :

Hamedo (1200 JP, Monk): If you are targeted by an ATTACK, BATTLE SKILL, THROW, or CHARGE directive and your attacker is within range of your weapon, the attacker's directive will be cancelled and you will instead execute an ATTACK directive on the attacker. Note that this only works on the above-listed commands, which means it is useless on monsters, since they have special forms of physical attack. This ability will trigger Br% of the time. Note: unlike Counter, Hamedo will activate against spell guns.