The expression “Zhangshouzhi shi zhengti zhi yong 長寿祇是証体之用” can be found in volume one of Chanjan's Commentary on the Fahua xuanyi. It indicates that the eternal life span of the original Buddha, revealed in chapter 16 of the Lotus Sutra, “The Life Span of the Tathagata was a benefit of having of touched perfect awakening. Chanjan interpreted Perfect Enlightenment as “zhufa shixiang 諸法実相 (The True State of All Elements)” prea-ched in Shakumon Sections of the Lotus Sutra.
In Japanese Medieval Tendai, the strange tendency to interpret Enlightenment as Innate Buddha-Nature (Original Enlightenment) appeared.
On the other hand, according to Nichiren, Enlightenment was understood as the Fundamental Truths of the Hommon Sections of the Lotus Stura. However, in the history of subsequent Nichiren religious group, the term was interpreted variously.
