Haven't had this fun in a while.
I want to say not that difficult too, expect it was a learning process.
That and Knell and I still do not know how to beat the final final part.
We are at a loss, and if you lose you lose all your continues and it's instant game over too :<
If you have any ears at all you'll probably recognize the two main character's voice actors.
Horie Yui and Kugumiya Rie.
I think if you unlock the third secret character she is voiced by Yuko Goto.
Seiyuu are pretty cheap!