MIA is a Main Story Quest in NieR: Automata.
"A group of YoRHa units headed to the surface has lost contact with command. Their black boxes are still online, so they are presumed alive. Investigate their last known location"
Second MIA quest:
"9S and other YoRHa units have been lost due to a large EMP. Use the scanner to find them"
- Find the missing YoRHa units.
- Defeat the Broken Machine
- Use your scanner to find surviving YoRHa units
- After completing The Machine Surge, head back to the Resistance Camp and obtain your free room
- Leave the Resistance Camp to trigger a conversation and receive the quest.
- Once you have the quest, walk left of the camp until you come across the destroyed highway, and look to your right until you see a passage between the blocked buildings. Use the ladder in the middle to go down to an underground area. Follow the tunnels, and look for a ladder, but don't go up yet. Continue forward to another ladder.
- Go up this ladder and into a large tree to obtain the weapon Virtuous Dignity.
- Now return down to the tunnels and take the ladder you avoided before. You will be in a large area with trees. Pick up the Shattered Earring and continue towards the nearby machines. The location Amusement Park will be revealed.
- Enemies here are mostly harmless, so you can ignore them and head up the stairs then take a right into a gate, and a left up a narrow back alley to reach an Access Point. Save then continue towards the mission objective by jumping on the broken thrill ride to get over the fence.
- Fight the Goliath Tank (Amusement Park)or be nice and ignore it. As long as you dont tank balloons with your face the tank doesnt actively attack you. It just drives around and sprays colourful things.
- go up the stairs and get on the Roller Coaster. Follow it until you drop down to a boss fight with Beauvoir.
- After the boss fight, exit to the start of the park and a peaceful machine will ask you to come to its village. Accept to gain access to the Machine Village. This opens the quest Machine Recon.
Second MIA quest (9S)
- Equip the A170: Scanner program on your Pod.
- Travel to the Flooded City and press L1. Your scaner will beep more frequently as you get close to a secret. It will reveal items and YoRHa units
- Go towards the red zone on the map to find 9S, but first your scanner will note a YoRHa by the side of a bridge. Next to it, a treasure weapon hides: Iron Will.
- Continue forward until you make it to the last platform. Here a YoRHa model will tell you they saw 9S get blown away and give you map coordinates direction you back to City Ruins. Head towards the City Ruins: Cave access point and the quest will go to 9S MIA again.
- The main boss in this area is an absolute pain. Bring your restorative items!