Unlock: Use Trevor, Complete Hang Ten
Requirements:
Out of the Frying Pan – Complete the whole mission with zero alerts.
Pyromaniac – Pour out the gasoline trail flawlessly in one try.
Use Josh's car and head to the marked location. Pull over to the leftside of the gate and use the car to jump over the wall. Utilize the jerry can to begin the gasoline trail from the grill, work slowly to cover the whole trail. Give the trail one good gunshot and escape by jumping over the wall.
The image featured at the top of this post is ©The Legend of Heroes: Trails of Cold Steel III key art.