Although markets did not react much to North Korea’s latest missile launch — which rocketed over Japan Friday morning — the chairman of the largest Japanese bank had a warning for his fellow citizens.

“We need to worry about this,” Nobuyuki Hirano, chairman of Bank of Tokyo-Mitsubishi UFJ and CEO of parent company Mitsubishi UFJ Financial Group, told CNBC on the sidelines of the Singapore Summit.

“Japanese citizens and public have been accustomed to a long-lasting peace, and they believe peace is always there, but this is not necessarily the case,” he added.

In fact, Hirano said, the recent string of missile launches — along with a massive nuclear weapon test that Pyongyang says was a hydrogen bomb — “gave us a very strong alert.”

Those provocations were “a kind of good lesson,” Hirano said, adding that now was the time for Tokyo, the U.S. and other countries to come together and make it clear that they would not allow North Korea’s “unlawful conduct.”