The incident in Otsu, the assassination attempt on the life of Tsarevich Nikolai Alexandrovich, occurred in the Japanese city of Otsu on April 29 (May 11) 1891. The heir to the throne, who was in Japan as part of an eastern journey, was attacked by police officer Tsuda Sanzō while returning to Kyoto after visiting Lake Biwa with two princes, Greek George and Japanese Arisugawa.

Tsuda rushed to the carriage in which the rickshaw was carrying Nikolai and managed to strike him twice with a saber. Although Nikolai's wounds were not too serious, his program during his stay in Japan was disrupted. On May 1 (May 13), Nikolai returned to the cruiser "Memory of Azov," where he celebrated his 23rd birthday, and six days later he departed for Vladivostok.

The Japanese government hoped for a death sentence for the police officer, using an extended interpretation of Article 116 of the Criminal Code, which provides for such punishment for crimes against members of the Japanese imperial family. However, under political pressure, the judiciary sentenced Tsuda Sanzō to life imprisonment. A few months after the verdict was delivered, he died in prison on Hokkaido Island.