Complete the indicated task to unlock the corresponding part.

All purchasable parts: Complete both the Collared and ORCA story modes.
White Glint Head, Core, Arms, Legs, and Head (top) Stabilizer: Complete the Defend Line Ark mission at the end of Chapter 2 (White Glint does not have to survive).
Salineos (split missiles) and 051ANNR (assault rifle): Complete the Defeat the White Glint mission at the end of Chapter 2.
07-Moonlight (laser blade), ASB-0710 (additional boosters shoulder piece): Defeat Orca Rank 5 Next Shinkai.
EC-0307AB (triple back laser cannons): Complete the Attack on Carpals mission in Chapter 3.