What rhetorical devices are used in the magnificent treasure in Wang Guozhen's Graduation?

The magnificent treasure in Wang Guozhen's Graduation is figurative rhetoric. Compare the classmate's "meeting each other late" to a magnificent treasure.

Original: "Graduation"

We set sail from here

Go to a distant place

As we move towards tomorrow,

How can you forget yesterday?

Looking back on yesterday

That lush day

It's always green

It always smells.

More than that.

Meet each other late.

That magnificent treasure

Today, we shed tears.

That's not sadness, that's singing.

Today, we broke up

This is not a loss, but a wealth.