Yusuf Zuck could only say that the Island Country had Ninjas, and from ancient times to the present, some schools in the Island Country had never stopped training Ninjas.
He had once read an article, mainly about the Island Country's Ninjas. The cost of training a Ninja in the Island Country was very high, and it also required starting from a young age, training their toughness, resolute character, and exceptional abilities.
There were even rumors that Japan's Ninjutsu could make a person disappear into thin air.
Back when he and Everest Zuck were dealing with Tripp Greer, Tripp Greer had thought he was a Ninja because only Ninjas could become Invisible.
And since there were such rumors among the people, they were probably true and indeed existed in reality.
The character for "Ninja" was also highly revered in the Island Country. When he was a child watching war movies, those rooms of the Island Country's military bigwigs all had the character for "Ninja" hanging in them.