The most interesting part is the Drop Gauge displayed on the bottom right of the screen when you play. When the Drop Gauge hits zero, the characters are switched. There is a time limit on the gauge and it seems that it cannot be replenished. So in that way you play as Sora to Riku, then from Riku to Sora, being forced to switch every few minutes. Also, if you press the start button the game pauses and you can press “DROP” button on the bottom screen. Doing that drains the drop gauge instantly and you can switch characters.
Furthermore, when you switch (from here on out I will refer to switching as “drop”), a screen pops up that shows the prizes, points, etc. that you accumulated during play. From there you can prepare the characters to your advantage for the next stage. For example, you can consume a potion that Sora collected and upgrade RIku’s magic power. Furthermore it seems that you’ll be able to utilize HP prizes here.
Well, in reality, being forced to switch characters like this is sort of tense and exciting. For example, you are in a boss fight with Sora, but then you drop to RIku and advance his storyline, but then you switch back to the boss fight with Sora, and you have to deal with an entirely different battle situation. Moreover, Riku and Sora are each off on their own separate adventures, but like the aforementioned links, you really get the feeling of “being together even when you are apart.” Because of the method gameplay being used to tell the story, more than any of the other titles before this you can really feel the connection between Riku and Sora.