I went ahead and played my way through this... for the most part, the story is slice-of-life, with a lot more focus on the comedic elements than in the main game. The result is a lot of hilarious scenes... and really little else for most of the first two-thirds of the game. The endgame story is supposed to be a tearjerking final battle... but to be honest, I hadn't developed enough affection for the new characters to feel anything for what was happening. Too much of the content was comedic, and as a result, there was more of an emotional disconnect than there was with the original game. While there were attempts to develop the new characters, the actual events were so... predictable (even by normal standards) that I just sighed in resignation and slogged through the last two battles (which were annoying as heck).
The actual battles themselves are much easier than the original, mostly because you start out with Touka's supreme boss-killer skills... in exchange, a lot of Corona's skills were harder to use because the MP consumption was increased (to be specific, from 35 to 77 for the single-enemy barrier-stripper). Aka is as OP as Corona, though in a more conventional way. She is the most powerful Red Elemental besides Ayumu, though she is more useful, since she has both Red and Black attacks.
For those who want more of Yumina's and Corona's cast's antics, this is an excellent fandisc... but for those who are already tired of the cast, it is probably more effort than it is worth.