We have already seen that Nichiren saw the Buddha’s pure land as immanent in the present world, based on the “Fathoming the Lifespan ” chapter of the Lotus Sūtra, which says, “I [Śākyamuni] am always in this Sahā world.” In the Kanjin honzon shō, Nichiren developed this idea specifically in terms of the origin teaching and the three thousand realms in a single thought-moment:
Now (ima) the Sahā world of the original time (honji) [of the Buddha’s enlightenment] is the constantly abiding pure land, freed from the three disasters and transcending [the cycle of] the four kalpas [formation, stability, decline, and extinction]. Its Buddha has not already entered nirvana in the past, nor is he yet to be born in the future. And his disciples are of the same essence. This [world] is [implicit in] the three realms, which are inherent in the three thousand realms of one’s mind.
In a manner very similar to that of the Sanjū shika no kotogaki and other medieval Tendai writings, this passage conveys the sense of the moment of enlightenment as accessing a timeless, “constantly abiding” realm in which all change is suspended. (Page 290-291)
Original Enlightenment and the Transformation of Medieval Japanese Buddhism