[A]s we receive the merits from the Buddha, the Great Mandala and the Odaimoku by devoting ourselves to them, we also send merits to them as well. How wonderful it is!
Our participation in the Buddha’s activities are also the activities of the Buddha residing in us and the activities of the nine realms residing in the Buddha’s life. This is the mutual possession of ten realms, Jikkai Gogu, and true cause and true effect, Hon-in Hon-ga. In other words, cause-and-effect, the realm of Buddha and the other nine realms are existing simultaneously and in oneness. Nichiren Shōnin stated in Kanjin
Honzon-Shō,

“All those who receive His (the Buddha) guidance are one with this Eternal Buddha,” (WNS2).

We are a part of the great life of the Eternal Buddha who has existed with the nine realms since the beginningless beginning.