The "Kaeraku-en Chronicle," which embodies the founding principles of Kaeraku-en, contains the keyword "一張一弛" (ichi-cho ichi-shi). This phrase originates from the teachings of Confucius in the "Book of Rites" and emphasizes the importance of not only being strict but also occasionally loosening up and enjoying oneself. In pursuit of nurturing exceptional talents, Saisho established the domain school, "Kodo-kan," in the 12th year of Tenpo (1841) and subsequently opened Kaeraku-en the following year. The Kodo-kan served as a place for both intellectual and martial training (一張), while Kaeraku-en offered a space for individuals to relax their minds and bodies during their leisure time (一弛). These two educational facilities were conceived as a pair, each complementing the other, to promote a well-rounded education system.(Translated from Kairakuen leaflet)