The area around foreign settlements had become quite dangerous due to the fact that ronin (masterless samurai) supporting the joi (expulsion of foreigners) doctrine began to congregate near the settlements at the end of Edo period, and as a result, incidents in which foreigners were stabbed to death became quite frequent.
居留地周辺は、幕末には攘夷浪人も出没して外国人殺傷事件がしばしば起こる物騒な地域であった。