Bertolt was the colossal Titan and he was the so he could tell if someone had the power of a Titan shifter

One night he saw you get spooked and you did put your hand to your mouth or protecting your nape in sparing. Bertolt saw this put tried to shrug it off and one night he could see the bite intense on your skin it was confirmed for him

You went outside and he followed you then he pulled you aside glaring at you

"I know what you are."