This paper deals with Nietzsche Kenkyu, which developed a philosophy of life (die Philosophie des Lebens) that connects individuals to the essence of life (Leben). The significance of the philosophy of life is shown in the present when our fundamental way of life is shaken by the rapid progress of science, technology, and computerization. In this dissertation, concepts such as intuition, will to power (wille zur macht), superman (übermensch), and self (selbst), which are related to the inner facts of life in Watsuji–Nietzsche’s theory, are elucidated by quoting Nietzsche Kenkyu, and the connection of these concepts with the inner nature of life is clarified. Nietzsche’s philosophy is the most direct ideological expression of internal experience as a pure life of self-expression and the creative activity of will to power. The will to life is the power that is working and becomes life itself.