Isshin, Two Heavens as One

If a creature attacking causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Magic Online Promos

Trained by the Imperials but disillusioned by their rigidity, he gave his heart—and his swords—to the Asari Uprising.

Kamigawa: Neon Dynasty

Kamigawa: Neon Dynasty Promos

Isshin's effect doesn't copy the triggered ability; it just causes the ability to trigger twice. Any choices made as you put the ability onto the stack, such as modes and targets, are made separately for each instance of the ability. Any choices made on resolution are also made individually.

Isshin, Two Heavens as One's ability affects only triggered abilities with conditions that are directly related to attacking, such as “whenever [this creature] attacks” or “whenever you attack with one or more creatures.” It does not affect triggered abilities with other trigger conditions, such as “whenever [this creature] becomes tapped.”