The Dark Chi Theme. It makes you feel not just the suspense of action sequences, but truly the emotion behind them too. Not only is it beautifully composed, but the musical flow typically goes PERFECTLY with whatever scene it's set against. Be it Chii's defending herself against Dragonfly or Hideki rushing into aHopeless Bossfightin order to play an RPG together with her. It's never inappropriate when used and it's always the perfect choice for the scene.
Yasashisa no Shouzou; a soft, slow piano and violin tune that manages to be sad, happy and sentimental all at the same time. Usually popping up in soft, emotional or sentimental scenes, the song is a Tear Jerker on its own.
Cult Classic: It has fallen into obscurity over the years despite being once one of Clamp's most popular works, but there's still a nostalgic fanbase that remembers its unusual charm.
Ear Worm: Ooh-ooh, ooh-ooh yeah. Ooh-ooh, ooh-ooh yeah. Ooh-ooh, ooh-ooh Let me be with you.
Fandom-Enraging Misconception: Referring to Freya as "Dark Chi(i)" (though she was called that a lot before her actual name was revealed) gets some fans riled up.
Hilarious in Hindsight: The view that the reader may have to empathise with a Japanese-centric worldview in order to enjoy the series becomes this when CLAMP released Gate 7 a decade later. That series requires readers to know their history on the Japanese Sengoku era.
Les Yay: With Chi's other self, her twin sister Freya.
Moe: Oh, Chi...So sweet and innocent and adorable.
Squick: Your tolerance for this series depends on how disturbing you find the premise.
Chi looks sixteen, acts like she's eight years old, and is an Innocent Fanservice Girl. It makes every moment of her nudity that much more awkward.
Chi's relationship with Hideki is played up as being "pure" and "innocent", but Chi is still heavily dependent on Hideki for many things and is as naive as a child. More often than not, they're more like Fatherand Daughter than anything else.
A lot of Chi's clothes come from Ms. Hibiya because Chi/Elda and Freya were built by her husband to be their surrogate daughters since she was infertile.
Minoru is 12, may not have parents, and is such a genius he knows how to build persocoms. Yuzuki is in a super modest maid's costume but his other four persocoms...are all busty women dressed in maid outfits so fetish they're essentially in bras or corsets with garter belts and a frilly apron. Minoru tells Hidelki they're "only computers" and not to get so aroused, nor that they put out. note He probably does it for the reaction he gets out of guys like Hideaki. He may have considered the whole thing an elaborate prank.
If you're disturbed by incest, then pretty much everything to do with Freya ends up being incredibly unsettling. While the series does play up how tragic her circumstances are, it's still a touch disturbing to hear a young girl talk seriously about falling in love romantically with her "daddy", especially since she seems to think that he might have loved her back if only he wasn't in love with her "mummy".
They Wasted a Perfectly Good Plot: One of the biggest bones of contention with this series is that it has no idea what it wants to be. The story ricochets from funny to serious to romantic so many times that the story eventually collapses under its own weight. And don't get started on the anime ending.
They Changed It, Now It Sucks!: The anime to the manga. The anime adds a lot of lightweight filler subplots and messes up the original chronology. Also, the mystery of Chi's reset button, or the program she had that was such a threat to Persocoms is never properly explained, and she has a cheesy fake death sequence that makes no sense.