In episode 479 of Naruto Shippuden from 15:00 to 16:10, there's a song playing when Naruto and Iruka are at the swing and a flashback plays.
What's that song?
It's the song that played when Minato saved Kushina. When Cloud ninja had kidnapped Kushina, Minato found her by the strands of hair she left on the trail. This is the song https://www.youtube.com/watch?v=6xR5FuBin_g&list=PLF7A13C44809B5893&index=100