[X] ".....me," you croak. "It was me."
There's a time for secrets and a time when they harm more than anything else. Sosuke needs to tell people, not because of pride or arrogance. It's because he's just become a high value target. There are only two ways of dealing with that. Obscurity, or ratcheting up the security. Basically he's going to need the support and resources increased fame would give him to survive and continue the fight.
Keeping it secret would have him become 'A guard' again. A famous guard yes, but one that has duties to guard someone else. And that's not going to be good when the enemy likely knows exactly what you're doing.