Darkness of Suzaku appear in the second playthrough after Chapter 6 has been cleared. In the Chapter 7, if you absorb any phantoma from defeating any enemies, you will have a small percentage to make him appear. When he appear in the world map, any phantoma you want to absorb will be going to the sky instead. When this happens, ride the Airship and approach him slightly underneath. What you need to do is simply shoots him until the Gil Multiplier and Gil Counter comes, Hold L button to brake, press R and Square rapidly to lock-on (blue circle appear) and shoot him. If your bullet connects, you will see a white circle appear as the impact. At first you won't be getting the Gil Multiplier and Gil Counter, but after you shoots a couple of times (I counted about 70 - 80 lock-on bullets, may need more or less) the Gil Multiplier and Gil Counter will appears. If your Gil counter doesn't appear, land nearby and fly again for the second attempt. Now shoots all the way until you have reached the maximum Gil (99,999,999). The whole process takes about 2 - 7 minutes, depends on how fast you stop at the good spot and how fast you shoot the bullets.
In-game Summer Costumes
Summer costumes can be unlocked as early as starting a new game. But before doing so, you must have a saved file of the demo version of the game in the memory stick being used as with the full release of the game. The saved file however must have contain the data for the costumes as were gathered from within the demo. There's a total of 14 costumes overall.