Shakyamuni Buddha in our heart leads to unshakable happiness

“It means to have a mentor in your heart while standing on your own two feet. President Toda resides in my heart. This is not something you speak out loud; it’s a matter of the heart. This is because unity is something that exists inside you.’ At all times, no matter where I am, I feel as if I am constantly engaging in dialogue with President Toda as I go about my activities. Our unity exists within me. This unity of mentor and disciple transcends distance and time...” -- Taisaku Ikeda

"When in one’s heart one takes faith in Namu-myoho-renge-kyo, the heart becomes a dwelling and Shakyamuni Buddha takes up residence there. At first one is not aware of this, but gradually, as the months go by, the Buddha in the heart begins to appear as in a dream, and one’s heart becomes bit by bit ever more joyful. Numerous are the teachings of Buddhism in this regard, but I will not go into them here."

"Moreover, passages in the sutra tell us that when demons have entered a person’s body, that person cannot take faith in the sutra, but when the spirit of Shakyamuni Buddha has entered one’s body, then one can believe in this sutra. When the reflection of the moon enters the water, the water becomes pure. In the same way, the reflection of the moon that is Shakyamuni Buddha, the lord of teachings, has entered the waters of your heart, [and your heart has become pure]. I find this most reassuring."

It is precisely because Daisaku Ikeda rather than Shakyamuni Buddha has entered their heart that they disbelieve the Sutra and the teachings of Nichiren. 

"If we examine the Lotus Sutra, we find it stated that, in cases like these, Shakyamuni Buddha enters into a person and inspires such determination in that person’s heart. It is like someone who, with no particular thought in mind, drinks sake and becomes intoxicated. After he is intoxicated, a quite unexpected desire arises in his heart and he is inspired to give away his belongings to other people. Although the person has all his life been stingy and greedy and is destined for rebirth in the realm of hungry spirits, because of the effect of the sake, he is able to enter the realm of a bodhisattva."