And in the Shozomatsu Wasan:

How difficult to renounce my evil nature...
My mind is like snakes and scorpions,
And since even the good I try to do
Is tainted with the
Poison (of self-centered effort),
It must be called the practice of an idiot.

Again, in the Ichinen Tanen Mon’i:

The term bombu means “ignorant being filled with base passions.” It refers to those who are continually filled with greed, anger, jealousy and a critical attitude that will not cease end until death.

As indicated in the above passages, because of his deep self-reflection that comes from the shinjin based on “Buddha-centered power,” the Venerable Master laments his “ignorance and base passions” and the evilness of his nature. He keenly realizes that he can never overcome that nature until his life in this world comes to an end. Accordingly, he strongly emphasized the fact that he was “deeply filled with evil” and unable to become a Buddha in this world, or even approach anything like one. This should be apparent from the “deep faith on the part of the being to be enlightened” (ki-no-jinshin) of the “two aspect of deep faith” (nishu-jinshin) in which realization that we are “deeply filled with evil” continues even after our shinjin is determined.

In the Chapter on Transformed Land of his Kyogyoshinsho, the Venerable Master wrote:

In the life-time teachings of Shakyamuni Buddha, attaining Enlightenment in this world is called following the Path of Sages and also the Path of Difficult Practices. ... Attaining Enlightenment in the Pure Realm of Serene Sustenance is called following the Pure Land Path and also the Path of Easy Practice.

As explained here, “becoming a Buddha” in this world is possible only by following the Path of Sages, and “becoming a Buddha” through birth in the Pure Realm of Serene Sustenance is called the Pure Land Path.

The Venerable Master included the following in his Jodo Wasan:

Tathagata is Nirvana;
And Nirvana is referred to
as the nature of Buddha.
An ordinary person
cannot be enlightened (in this world),
But can realize it
In the Land of Serene Sustenance.

In the Nyashyutsu Nimon-ge (Hymns on Entering and Leaving the Twin Gates), is the following:

Those “filled with base passions” can attain Nirvana without cutting off their base passions. ... This is the virtue of the natural Nirvana (as opposed to Nirvana attained by cutting off base passions).