Completion Bonus
Successfully complete the game and save it after the credits complete. Start a new game to being with the items obtained in your previous attempt.

Jackson
Successfully complete the game in hard mode with an "A" or "S" rank (collect all elves). Start a new game from this saved game to being with all elves including Jackson. Alternately, collect and power-up all cyber elves without using any of them under the normal difficulty setting.

Ultimate Mode
Unlock Jackson and start a game. Successfully complete the game using all elves. Hold R when starting a new game to play in ultimate mode.

Easy weapons Level-Ups
After completing the introductory level where Zero gets his Sword and Pistol, get on the teleporter and teleport back to the base. Immediately exit the place by trying to climb the ladder you are in front of. Ciel will talk to you, and give you several options to select. Keep selecting the first choice she gives you on each option and you will be teleported to a junkyard level. In the middle of the level there will be these pillars that will keep growing back after each segment is destroyed. You can keep destroying the segments with the Sword and Pistol and they will level-up. Keep destroying the segments until the Sword and Pistol are at their maximum levels.

To maximize the skill level of all the weapons, use them at the enemies at the disposal center; at the part where two spiked things spring up and shoot energy bolts horizontally.

Defeating X Second Form With The Z-Saber
Upgrade your Z-Saber skill to the fifth or sixth level to charge it faster. When fighting X second form, use the Ice Chip (obtained from one of your missions), charge your Z-Saber, climb any of the two vertical platforms, and jump-slash towards X's head. Be careful when jumping at X's head as you may hit X's hand.