The Ōtsu incident (Japanese: 大津事件, Hepburn: Ōtsu Jiken) was an unsuccessful assassination attempt on Nicholas Alexandrovich, Tsarevich of Russia (later Emperor Nicholas II of Russia) on 11 May [O.S. 29 April] 1891, during his visit to Japan as part of his eastern journey.

Tsarevich Nicholas had travelled by sea to Vladivostok in Far Eastern Russia for ceremonies marking the start of construction of the Trans-Siberian Railroad. A visit to Japan formed part of this trip. The Russian Pacific Fleet, with the Tsarevich on board, stopped in Kagoshima, then Nagasaki, and then finally Kobe.

From Kobe, the Tsarevich journeyed overland to Kyoto, where he was personally met by a high-level delegation spearheaded by Japanese Prince Arisugawa Taruhito. This was the first visit to the region by such a figure since Prince Heinrich of Prussia visited in 1880, and, two other British princes who had visited in 1881. At the time of the Tsarevich's visit, the military influence of the Russian Empire was growing rapidly in the Far East, viewed as the catalyst responsible for prompting the Japanese government to place heavy emphasis on this visit, principally to foster better Russo-Japanese relations.

Nicholas showed interest in the Japanese traditional crafts, and reportedly received a dragon tattoo on his right arm. Nicholas had read Pierre Loti's Madame Chrysanthème before arriving in Nagasaki, and in imitation of a character in that text, Loti also had a dragon tattooed on his right arm. Nicholas is also thought to have bought an ornamental hairpin for a Japanese girl of unknown status.

The assassination attempt occurred on 11 May [O.S. 29 April] 1891, while Nicholas was returning to Kyoto after a day trip to Lake Biwa in Ōtsu, Shiga Prefecture.

He was attacked by Tsuda Sanzō (1855–1891), one of his escorting policemen, who swung at the Tsarevich's face with a sabre. The quick action of Nicholas's cousin, Prince George of Greece and Denmark, who parried the second blow with his cane, saved his life.

Tsuda then attempted to flee, but two rickshaw drivers in Nicholas's entourage chased him down and pulled him to the ground. Nicholas was left with a 9 centimeter long scar on the right side of his forehead, but his wound was not life-threatening.

Nicholas was rushed back to Kyoto, where Prince Kitashirakawa Yoshihisa ordered that he be taken into the Kyoto Imperial Palace to rest, and messages were sent to Tokyo. Fearful that the incident would be used by Russia as a pretext for war, and knowing that Japan's military was no match for Russia at the time, Prime Minister Matsukata Masayoshi advised Emperor Meiji to go immediately to visit the Tsarevich. The Emperor boarded a train at Shimbashi Station, and traveled through the night so as to reach Kyoto the following morning.

The following day, when Nicholas expressed a desire to return to the Russian fleet at Kobe, Emperor Meiji ordered Prince Kitashirakawa and Prince Arisugawa Takehito to accompany him.

Emperor Meiji publicly expressed sorrow at Japan's lack of hospitality towards a state guest, which led to an outpouring of public support and messages of condolences for the Tsarevich.

More than 10,000 telegrams were sent wishing the Tsarevich a speedy recovery. Sanzō's home town in the Yamagata Prefecture even legally forbade the use of the family name "Tsuda" and the given name "Sanzō". When Nicholas cut his trip to Japan short in spite of Emperor Meiji's apology, a young seamstress, Yuko Hatakeyama, slit her throat with a razor in front of the Kyoto Prefectural Office as an act of public contrition, and soon died in a hospital. Japanese media at the time labeled her as "retsujo" (lit. valiant woman) and praised her patriotism.^[1]

The government applied pressure to the Court to try Tsuda under Article 116 of the Criminal Code, which demanded the death penalty for acts against the emperor, empress or crown prince of Japan. However, Chief Justice Kojima Korekata ruled that Article 116 did not apply in this case, and sentenced Tsuda to life imprisonment instead. Although controversial at the time, Kojima's decision was later used as an example of the independence of the judiciary in Japan.^[2]

Accepting responsibility for the lapse in security, Home Minister Saigō Tsugumichi and Foreign Minister Aoki Shūzō resigned.^[3]

The Russian government officially expressed full satisfaction in the outcome of Japan's actions, and indeed formally stated that had Tsuda been sentenced to death, they would have pushed for clemency; however, later historians^[4] have often speculated on how the incident (which left the Tsarevich Nicholas permanently scarred) may have later influenced Nicholas's opinion of Japan and the Japanese—as well as how this may have influenced his decisions in the process up to and during the Russo-Japanese War of 1904–1905.^[5]

The former policeman Tsuda was sent to Abashiri Prison in Hokkaidō, and died of an illness in September of the same year. His motivation for the attack remains unclear, with explanations ranging from mental derangement^[6] to hatred of foreigners.^[7]

• The rickshaw drivers who captured Tsuda, Mukaihata Jizaburo (1854–1928) and Kitagaichi Ichitaro (1859–1914) were later called to the Russian fleet by the Tsarevich, where they were feted by the Russian marines, given medals, and a reward of 2,500 yen plus an additional 1,000 yen pension, which was a tremendous sum for the time. They were celebrated in the media as national heroes. However, during the Russo-Japanese War, the admiration of their friends and neighbors turned sour, they lost their pensions, were accused of being spies, and had to suffer harassment from the police.
• In 1993, when the Russian government was attempting to verify whether or not bone fragments recovered from the Yekaterinburg murder site belonged to Tsar Nicholas II, a sample of the Tsar's DNA was required. Relics from the Ōtsu Scandal were examined to see if enough blood stains were present to make a positive identification possible, but the results were not conclusive.^[8]

• Rotem Kowner. "Nicholas II and the Japanese body: Images and decision making on the eve of the Russo-Japanese War". The Psychohistory Review 26, 211–252.
• Yoshimura Akira. Nikolai Sounan. Tokyo: Iwanami Shoten, 1993. ISBN 4-00-001700-4. (in Japanese)
• Keene, Donald (2005). Emperor Of Japan: Meiji And His World, 1852–1912. Columbia University Press. ISBN 0-231-12341-8.