Gansu
missing from the end of 'Zuko Alone'
Gansu found Sensu, as he was being discharged from the army; he'd been wounded and left for dead when his battalion had been captured. His son was still weak and would forever walk with a limp, but he was alive; that's all that mattered.
When they returned home, Gansu learned what that unnamed teenager had done after he'd left. Saved Lee from the thugs in town… and revealed his true identity.
That night, at the family shrine, Gansu spoke of Zuko. "Spirits… he's Fire Nation. But he saved my youngest.
…I could tell he's lost. Help him find his way."