Kūkai(774-835) is commonly known as Kōbō daishi, an honorific title given to him by the Heian court. Kūkai is one of the most respected and popular Buddist masters of Japan. He is remembered as the founder of Shingon or Esoteric Buddhism of the monastic center on Mt. Kōya. Legends about Kūkai are still being told all over the country, especially in the western part where he grew up and spent most of his life.. The purpose of this study was to explore the meaning of Kūkai's turning point (his commitment to Buddhism) in adolescence in his twenty-four. Kūkai wrote The Rōko shīki(Indication of the Goal for the Deaf and Blind) to show the superiority of Buddhism over both Confucianism and Taoism. Kūkai was so bold as to rank Buddhism higher than Confucianism, the intellectual orthodoxy of the time. He attempted to persuade the reader that Buddhism alone can satisfy man's spiritual aspirations. He rewrote The Rōko shiki in The Sango shīki (the Goal of the Three Teachings) about 20 years later. Comparing two books, we noticed the meaning of Kūkai's turning point being different depending on two books. He was telling the turning point which is being experienced actually by The Rōko shīki, and was telling the meaning of the recalled turning point the after time by The Sango shīki. As a result, the difference as The Rōko shīki which marked "the end of something" and The Sango shīki. which drew "the start of something" was suggested in the process of turning point in adolescence.