Hakuin Ekaku was one of the most influential figures in Japanese Zen Buddhism, who regarded bodhicitta, working for the benefit of others, as the ultimate concern of Zen-training. While never having received formal dharma transmission, he is regarded as the reviver of the Japanese Rinzai school from a period of stagnation, focusing on rigorous training methods integrating meditation and koan practice.

Zen is a school of Mahayana Buddhism that originated in China during the Tang dynasty as the Chan School or the Buddha-mind school, and later developed into various sub-schools and branches. From China, Chán spread south to Vietnam and became Vietnamese Thiền, northeast to Korea to become Seon Buddhism, and east to Japan, becoming Japanese Zen.