[kenshin]

Superior Weapon Mastery (10251) str+2, spd. +25%, P.atk. +376 and p.accuracy +3 when a sword, blunt, or spear weapon is equipped. Increases the number of possible targets during a spear attack. 50% chance of triggering Lightning Force during a critical attack. Additionally, there is a chance the re-use time of skills will reset or the duration double depending on your str.

As description, this skill has 50% chance of triggering Lightning Force during critical attack.

But when we test, even with normal attack without using skill or using skill but no critical, Lightning Force is still triggered.