You were a Marleyan. You were also friends with Zeke, as well as his younger brother, Eren.

You were strolling down a town, and then you see Zeke. You find nothing of it but then you see Eren running up to Zeke with a flashbang.

"Yeager bomb!" Eren yelled before he threw the flash and in Zeke's face and then ran. You ran off as quick as you can, knowing that when the brightness goes away, he'll transform into his titan.