What does the title of the song "The Last One in Your Heart" mean?

When I was young, I was madly in love with you, and if I happen to think of you one day years later, with a mind that has been through the world and has been baptized in oil, salt, and vinegar, I will still look at you again, but I will still have red eyes, because at that time, the one who is not qualified to talk about the future has already engraved you in my future, and even if I am dying in the future after a few decades, don't worry... The white-haired one will definitely remember the black-haired one, and love the white-haired one.

This is the lyrics, the title of the song is "the last one in your heart"

Seeing the dissolving clouds slowly blooming broken time sliding along the umbrella playing down the war resting in the heart praying for a cover a sheepish loneliness are fogged up on the empty stage lone conductor in front of you to play a I had suspected that it was an illusion potion please Chopin rubbed lies please Li Bai to tell in your hands to sleep a little bit with the heart-warming wounds scabbed over. Sing with the birds, step with the leaves and sleep with your smile, and make a flower with a guardian's scab.