I think a new character like Miyuki is necessary. Kana is already somewhat pathetic enough as it is, leeching Chiaki's dumber friends or Touma as her own. Without Miyuki, Kana really just has Keiko (Fujioka doesn't count), and we all know that Keiko really just tolerates Kana. Sure, they all interact with each other's friends, but Kana needed another one her own age. Even so, Kana's attempts at manipulation by proxy have backfired, and she has created a monster who uses puppy eyes to get what she wants.

I had forgotten that Chiaki's angel side looks pretty much like she does but more polite, but her devil side is an adult with a chest the size of Haruka or slightly greater...and both of them usually come to the same evil conclusions.

I don't expect much out of this series, and they tell you not to anyway.