Lupin III: Island of Assassins

Lupin III and Zenigata are both at a politician's birthday party, where a fake Lupin calling card has been left behind. The situation escalates when masked assassins break in and Lupin and Zenigata get caught up in the crossfire. After Zenigata is shot, Lupin recognizes the Walther P-38 used in the attack as his own gun, which leads him to investigate further. It turns out the assassins are from a secret island called the Island of Assassins, where corrupt government officials use them for their own interests.