Day 16 concludes Chapter 11, Beholding the Stūpa of Treasures, and completes the Fourth Volume of the Sūtra of the Lotus Flower of the Wonderful Dharma.

Having last month witnessed Śākyamuni purifying the Saha-World to seat his replicas, Śākyamuni asks in gāthās who will protect this teaching.

(The Buddha said to the great multitude.)
Who will protect
And keep this sūtra,
And read and recite it
After my extinction?
Make a vow before me to do this!

Many-Treasures Buddha,
Who had passed away a long time ago,
Made a loud voice like the roar of a lion
According to his great vow.

Many-Treasures Tathāgata and I
And the Buddhas of my replicas,
Who have assembled here,
Wish to know who will do [all this].

My sons!
Who will protect the Dharma?
Make a great vow
To preserve the Dharma forever!

Anyone who protects this sūtra
Should be considered
To have already made offerings
To Many-Treasures and to me.

Many-Treasures Buddha vowed to go
About the worlds of the ten quarters,
Riding in the stūpa of treasures,
In order to hear this sūtra [directly from the expounder].

Anyone [who protects this sūtra] also
Should be considered to have already made offerings
To the Buddhas of my replicas, who have come here
And adorned the worlds with their light.

Anyone who expounds this sūtra
Will be able to see me,
To see Many-Treasures Tathāgata,
And to see the Buddhas of my replicas.

Nichiren offers this comment on appearance of the Stupa of Treasures:

We do not see a shadow in the dark. Man does not see a flight path of a bird in the air. We do not see the path of a fish in the sea. We do not see everyone in the world reflected on the moon. However, a person with “heavenly eyes” sees all these. The scene of the chapter “Appearance of a Stupa of Treasures” exists in the mind of Lady Nichinyo. Though ordinary people do not see it, Śākyamuni Buddha, the Buddha of Many Treasures and Buddhas throughout the universe recognize it. I, Nichiren, also can see it. How blessed are you!

Nichinyo Gozen Gohenji, A Response to My Lady Nichinyo, Writings of Nichiren Shōnin, Volume 4, Faith and Practice, Page 138