Watching the first couple of episodes of Kanon gives one the feeling this is simple and slow paced but well delivered anime. Yuuichi, our well meaning protagonist, is moving in with his cousin Nayuki and her mother Akiko for a school term while his parents are abroad working. These episodes are also an introduction to the eclectic cast of nuclear-grade cute packing girls of Kanon.
Yuuichi seems a little reluctant to be switching schools and moving to the town he last visited 7 years ago, but, that seems entirely normal. Even the fact he finds an item he can't remember packing with his belongings seems fairly normal.
BAM! Kanon introduces the character, Mai, and her hobby of prowling, sword in hand, the school hallways at night. Suckered into the show by what you probably assumed is your standard (if somewhat serious and lacking in humour) Love Hina or Tenchi Muyo! scenario you're sent with poor Yuuichi down an emotional roller-coaster of grief. Yuuichi struggles to sort out why he has selective amnesia about the events 7 years ago while helping the girls of Kanon with their problems.
Yamaguchi Ryouta and Nakamura Makoto who came up with the concept for Kanon are a seriously twisted people. Most shows would make do with a single really emotional incident. Kanon, after hooking you into caring about a character which on the surface seems normal gives them a disaster for Yuuichi and her to play with and shoves them down the grief roller-coaster. My jaw dropped and I got the sniffles more than once watching Kanon. Watching Kanon episodes back to back is not recommended for the emotional!
Technically the show is very well done. The animation is smooth and avoids the common digital flaws. The music fits the mood of the series perfectly. The interleaving of the many storylines for each of the girls's problems works well, but, since Yuuichi is generally the only character common to each one (except for his own story) it gets a little confusing at times. Compounded with the sheer number of characters outnumbering the number of episodes makes Kanon the "Russian novel of anime".
For an anime series based on a hentai dating game it is rather tame. Yuuichi avoids groping any of the girls the entire series. He does end up kissing two girl and ending up in bed (in a totally platonic sense!) with another so I'd hardly recommend this to anything less than a teen audience.
I was a bit disappointed in Yuuichi's character as he never really develops. I suppose the idea was to use the dating simulator standby that a blank slate character makes it easier to empathize and imagine yourself as him. However, the loss of choose in what a character does in an anime takes so much of that type of empathy away. I hardly saw the point to it.
Overall, Kanon's continual disaster mode after the introduction episodes got a little tiring. The clever plot twists, near perfect foreshadowing and the doozy of a good ending made it all worth while for me. If the above review sounded interesting and you have a box of tissue handy then I highly recommend Kanon.