"Grandmaster of the Six Samurai's" second effect targets 1
"Six SamuraI" monster in your Graveyard. If
"Grandmaster of the Six Samurai" is in your Graveyard, it can target itself.
If
"Grandmaster of the Six Samurai" is destroyed by your opponent's card effect while in your hand or your Deck, its effect activates.
If you Special Summon
"Grandmaster of the Six Samurai" and your opponent negates the Special Summon and destroys it with their
"Royal Oppression",
"Grandmaster of the Six Samurai's" effect activates. If your opponent uses the effect of your
"Royal Oppression" to negate the Special Summon,
"Grandmaster of the Six Samurai's" effect does not activate.
If your opponent activates an effect to destroy one of your
"Six Samurai" monsters and you use the effect of the
"Six Samurai" monster to destroy your
"Grandmaster of the Six Samurai",
"Grandmaster of the Six Samurai's" effect doesn't activate because it was destroyed by your
"Six Samurai" monster and not by your opponent's card effect.