Tsunami
Characters: Korra, Mako, Bolin, Caloway (OC), Iroh, Asami, Tenzin, Ikki, Jenora, Meelo, Pema, Rohan, Lin Beifong.
Summary: The characters are telling their story after experiencing a natural disaster of water during a vacation.
Character ages during tsunami
Korra: 21
Mako: 22
Bolin: 20
Caloway: 19
Iroh: 25
Asami: 22
Tenzin: 55
Ikki: 11
Jinora: 14
Meelo: 9
Pema: 39
Rohan: 4
Lin Beifong: 54
I'm only unsure about Iroh's age because his avatar wiki page just says young adult under his age. But, it's pretty explanatory that it's 4 years after the whole Amon thing.
Character ages during story telling
Korra: 25
Mako: 26
Bolin: 24
Caloway: 23
Iroh: 29
Asami: 26
Tenzin: 59 (would be, but died during)
Ikki: 15
Jinora: 18
Meelo: 13
Pema: 43 (would be, died of heartbreak after a year without Tenzin)
Rohan: 8
Lin Beifong: 58 (would be, but died of natural causes 3 years later)
