"Yugen and Mono-Ai" is a classic aesthetic work by Krei Onishi. From the perspective of traditional Japanese aesthetics, he conducted theoretical research and discussions on "Yugen" and "Mono-Ai", trying to break the framework of Western aesthetics and incorporate Japan's unique aesthetic concepts. "Yugen" is a subtle interest that is difficult to explain in words. "Monoai" is often used to express the consciousness and connotation of Japanese national aesthetics. By interpreting yugen and monoai, we can reach the quiet depths of Japanese and even Eastern aesthetics.