The sound of the alarm only sounded on a small box-shaped device located next to the heads of the soldiers who inhabit this secret base.
The purpose, of course, is so that the intruders who set off the alarm won't know they did. So they didn't have time to run away.
Soldiers and LTC. Coil immediately rushed to the LTC. Ibis' room where the alarm came from. But when they got there the door was tightly shut.
They heard a noise from inside. But when they opened the door, all they could see was a messy room and LTC. Ibis lying on the floor unconscious.
LTC. Coil approached him. His face was clearly wounded from the few punches. That means someone did infiltrate here and managed to beat him up.
LTC. Coil only had one guess as to who was in here, making the whole room fall apart as if he was looking for something haphazardly, beating up LTC. Ibis then just ran away.
Inside this room is the crystal key belonging to the Elves. LTC. Ibis insisted that he keep it in the first place.