Shijaku KATSURA (the second) constructed a theory that a laugh is drawn by release of tension, and in keeping with his theory, he classified the ochi of rakugo into four categories.
桂枝雀(2代目)は笑いは緊張の緩和によって起こるという理論を立て、それと平行して落語の落ちを4種類に分類した。