The attacks came as no surprise, the very moment the villain squad had entered the city section of the training grounds. Their opponents were thus far an Archer, a speedster, and someone tossing rocks. The first two weren't a threat to his mass but the rock thrower, if it was a quirk, could be trouble. 
Having failed to see where the Archer and the rock tosser had been when they fired, it meant scouting around looking for them.

Or waiting till they attacked.

A quick burst of expended energy sent Midnight far to the right, a roll later across the pavement and he was at the nearest many storied buildings lowest level. Another quick burst of energy turned whatever locking mechanism was securing the doorway into melted scrap strewn across the floor.
Once inside, caring not at all for the other villains in his team, his wild chase went up 5 flights of stairs with his minor levitation, depositing himself at a window under cover of a cement pillar to block anyone from getting a good glimpse of the shifting multicolored villain.

Down below he could see Dieselpunk getting ready for combat and waited for a chance to spot their unseen prey and pounce.