The Kaisei Academy is a preparatory boys private secondary school located in Arakawa ward, Japan.
Founded in 1871, the Kaisei Academy has produced a large number of noted alumni. Every year three hundred students are admitted to its junior high school, and one hundred students to its high school. The school's primary policy is 質実剛健 (Shitsu-jitsu-gou-ken), which means strong, simple, or spartan. The school policy is well represented in its school events such as an athletic meeting, marathon, swimming summer school, annual boat race with Senior High School at Otsuka, University of Tsukuba.
The school, which has produced many notable alumni, was founded in 1871. At first, it was established as a Kyōryū Gakkō of the prepschool to Senior school such as First High School. After WWⅡ, this school was integrated into the University of Tokyo.) Its motto is "The pen is mightier than the sword", and is often known by the Japanese abbreviation "pen-ken" (pen-sword).
- Okada Keisuke, (1868 – 1952) Prime Minister from 1934-36 / Temporary on the register In the prepschool age
- Ikeda Kikunae, (1864 – 1936) who identified the flavour umami / In the prepschool age
- Physicist Nagaoka Hantarō, (1865 – 1950), who developed the Saturnian model of the atom / In the prepschool age
- Poet Masaoka Shiki, one of the "four great masters" of the haiku / In the prepschool age
- Poet and author Shimazaki Tōson (1872-1943), leading figure in the Meiji Romantic movement. / In the prepschool age
- Admiral Akiyama Saneyuki (1868-1918), planner of the Japanese strategy at the Battle of Tsushima / In the prepschool age
- Vice Admiral Yamaguchi Tamon (1892 - June 4, 1942), commander of the aircraft carrier Hiryū at the Battle of Midway
Coordinates: 35°43′57″N 139°45′54″E / 35.73250°N 139.76500°E