Enter "RO-SA-MI i" as a case-sensitive name.
Achieve a 100% game completion.
Purchase and complete Route E. Purchase and complete Route F with a character from One Year Wa. Defeat the Psyco Gundam and the Psyco Gundam MKII in Route A. Purchase the Psyco Gundam and the Psyco Gundam MKII in the collection shop. Then, purchase items 1, 2, 4, 6, 8, 9 in the specials section. You can now purchase ZZ Gundam.