As I mentioned in my last post, there are somewhere around three hundred Psych Pins in The World Ends With You. As such, simply acquiring all of these Pins is a fairly significant aspect of the game. You even get rated on how many Pins you have mastered as one of the completion rankings in the save screen. All told, this is one aspect of the game that has probably eaten more of my time than the main plot.
There are four ways to acquire Psych Pins in the game. The most obvious way is to buy them from shops, which is fairly self-explanatory. The second way is to acquire them from plot scenes and various other story events in the game, which are actually surprisingly generous in this game. You can get a lot of great Pins and other items just by going through the game's story and opening up all the paths between the game areas, which is very nice and makes up for the game's lack of typical exploration-based rewards like the classic treasure chest. These two are simple enough, but the other two ways you get Pins are a bit more unique.
The third main source of Psych Pins is the Noise, the main enemies of the game. Normally, I hate trying to gather items that are randomly dropped by enemies in RPGs, but The World Ends With You puts an entirely new spin on this concept that makes it useful and fun. Basically, the game enables you to control your acquisition of Pins from the Noise to a very high degree. Every Noise has exactly four Pins it could possibly drop, one for each difficulty level, and a set probability for dropping each Pin. Whenever you beat that Noise, the game randomly determines which Pin the Noise drops, starting with the difficulty level you are currently playing at and going down from there until either you get a Pin or it runs out of difficulty levels to check. What is more, you know these drop rates for every Noise that you have defeated, and you know which Pins you have acquired from which Noise and the difficulty level they are associated with. On top of this, you can freely set the difficulty level at any time, and each area of the game has a fairly limited number of Noise at any one time (and different groups of Noise have different icons on the game screen, making it even easier to isolate them), so it is possible to control both what enemies you are fighting and which Pin those enemies are most likely to drop. If you want a Pin that is only dropped by a certain Noise on High difficulty, then you can easily find that Noise and fight it on High difficulty whenever you want (unless you have passed the point in the game where that Noise is replaced by other Noise, which happens). This is already a significant improvement over fighting a hundred random battles in hopes if finding a rare enemy who will only drop a kind of item with a 1/128 chance, but it gets even better still.
One of the real marvels of The World Ends With You's combat system is that you can vastly increase the odds of an enemy dropping an item, simply by taking on a handicap. At the bottom-right corner of the menu screen is a star rating, that serves as a multiplier for the drop rates for every Pin in the game. By voluntarily lowering your level below its maximum value (which you can do or undo at any time outside of battle), you can increase this star rating by one for each level you give up. If an enemy starts with a default drop rate of 2% for a certain pin, then decreasing your level by 9 will lead to a star rating of 10, which gives you an adjusted drop rate of 20%. What is more, by challenging enemies to chain battles (a sequence of battles in which you don't heal between battle like you normally do), you multiply the star rating by the number of battles in the chain. If you fight a three "reduction" chain battle, with the same enemy and level handicap as before, the star rating temporarily increases from 10 to 30, and the drop rate further increases from 20% to 60%. By taking on additional challenges, you transform a long-shot drop rate of 2% into a nearly guaranteed 60% chance. Combined with the elements I described in the paragraph above, this transforms the task of acquiring rare Pins from a matter of dumb luck into something that can easily be accomplished by good planning and effort, rewarding skill with the game rather than a high tolerance for frustration. The only barrier to getting the Pins you want is your ability to win battles, rather than how much time you are willing to put into the task. It turns a chore into a fun puzzle to sort out and a challenge to overcome.
A notable aspect of this system is that it even applies in boss battles. Actually, for normal boss battles, this may be something of a flaw. You can't tell the enemy drop rates until you have defeated the boss once, but you only ever fight the game's bosses once (at least, so far in my playthrough). It would probably work better if the drop rates for all of a boss's PIns were 100% by default, so you are guaranteed to get a Pin from the boss and what Pin you acquire is determined only by what difficulty level you have set when you fight the boss. However, the game's various optional bosses which you can fight endlessly are a different matter entirely. Their mix of very high challenge, extremely low drop rates, and valuable rare of even unique Pin drops seem designed to test your ability to manage this system, and they succeed at that task very well.
Also, the various battles against Pig Noise are worthy of note, though these are mostly just special battles that operate under special rules and are guaranteed to give you certain Psych Pins regardless of what your difficulty level or level handicap are set to. I really don't have much to say about them other than that I like them in general, but I get frustrated with how some are poorly designed (such as requiring a specific Pin that is not available during the period that the Pig Noise must be defeated in).
The final method that you use to acquire Psych Pins is Pin Evolution. Some Pins have the capability to transform into more powerful Psych Pins when they level up, based on the kind of Pin Points used to level them up. This gets a bit complicated, really, so I think I will skip my usual summary of the system and just mention some of my thoughts about it all. Put simply, I think this is one of the places where the game simply lets itself add a lot of complication for fairly little benefit. In order to use this system, I had to draw up a Pin Evolution chart based on information from a FAQ at GameFAQs.com, and I need to reference this chart practically every time I play the game. I find that doing so is practically a necessity, since even with the chart I have to devote myself to hours of work in order to get Pins to evolve, and it would be easily three time as much work without that resource. What is more, even the work I am putting in to this task isn't enough to get the 100% Pin Mastery rating, because that only counts Pins that have been mastered, but Pins that evolve don't count as being mastered. Most importantly, the large amount of effort required to level up and evolve Pins means that actually using Pins that have been mastered (and thus freely building the Pin Folders you want to use) will prevent you from ever acquiring a lot of the most useful and fun to use Pins in the game. This hurts the game more than it really helps, and runs counter to many of the other fairly ingenious elements of the game design.