If you're a scout: Erwin had assign you along with Amillia to go along with Eren and the others in luring the female titan in the underground while in human form. Focus on your task.

If you're a Garrison: You volunteered to one of the Scouts if you could help and you being a trustworthy person, they let you help. Just help the scouts in capturing Annie.

If you're an MP: Regardless if you're a rookie or not, you have no idea what's going on so you evacuated the citizens. However, while doing that, you watched the whole fight between two titans and decided to confront one of the scouts about this. Whatever your confrontation is.

For titans inside the wall: You are one of the few who found out about this regardless the regiment you belong to.