Activate this card after your opponent has targeted your monster. If you activate this card before they have targeted, they can target the monster you Special Summon from your Graveyard.
Your opponent has activated a "Fiendish Chain", and you only control a "Bujin Mikazuchi". You activate "Bujinfidel", and Special Summon "Bujin Yamato" from the Graveyard. Your opponent then targets your "Bujin Yamato" with "Fiendish Chain", as its effect resolves.