Simply have faith is the way to attain Buddhahood

The sutra known as the Lotus Sutra is a scripture that has no match among all the sacred teachings of the Buddha's lifetime. And, as indicated by its words "between Buddhas," it can only be understood between one Buddha and another. Those at the stage of near-perfect enlightenment or below, on down to ordinary mortals, cannot fathom it. This is why Bodhisattva Nagarjuna stated in his Treatise on the Great Perfection of Wisdom that persons below the level of Buddha should simply have faith, and in that way they can attain Buddhahood. 24/10

The Writings of Nichiren Daishonin
Reply to the Mother of Ueno
Written to the lay nun Ueno on October 24, 1280