Kurau is a cheerful twelve-year old girl living on the moon with her father, a professor who researches a mysterious energy source. While watching one of her father's scientific experiments, she gets hit by an an energy blast which disintegrates her fully. Kurau reappears as the fusion of herself and an alien sentient force, calling herself "Rynax", and gains extraordinary powers, like flying; walking through walls; and shooting powerful blasts of energy. Rynax come in pairs however, so another Rynax lies dormant in Kurau's body, and the waking Rynax is unable to give it up.
Kurau's mind appears to have merged with the alien entity as well, to the shock and grief of her father. During subsequent experiments, Kurau's powers involuntarily cause the young girl to seriously injure her father, an event which proves to be very traumatic. Her father still deeply cares for his half-alien daughter, but decides that it is best that he and Kurau are separated, so he sends her to earth to live with relatives.
Ten years later Kurau makes a living by performing dangerous covert operations as a freelance mercenary, in which her Rynax strength comes in handy. She has to hide her powers from the public as to not attract attention from the GPO, an organization out to capture all "Rynasapiens", i.e. people affected with Rynax powers. Since her Rynax-pair hasn't found the strength to come out yet in all those years, Kurau also feels incomplete and utterly lonely.
Then one night, in a flash of light, her pair suddenly appears out of her body in the shape of a teenaged girl, who looks much like herself. Kurau calls her "Christmas" and her happiness knows no bounds, until she discovers that the GPO has found out about them. Kurau and Christmas have to run from the GPO, helped by Kurau's father and a mysterious ex-GPO member called Doug.
Kurau: Phantom Memory was pretty much a "sleeper" title when it was released in 2004, being overshadowed by other popular anime titles during that period. Since then it has gained a reputation as a classic though, with a heart-warming and dramatic plot, well-rounded characters and beautiful animation. It's a must-see for people who like their "hard" sci-fi to go along with believable human relationships.
These examples are released into the wide, wide world:
- Barbie Doll Anatomy: There's just about no fanservice in the show, but clinical nudity gets this treatment.
- Bifauxnen: Kurau, a short-haired woman who could easily pass for a man.
- Bittersweet Ending: Ultimately averted. It may seem sad when Kurau saves the world from the Rynax and loses her own Rynax in the process. However, the world is back to normal, with happy endings for all the main characters. Even the Rynax were led to a new "vast world" where they wouldn't be a danger to humans or be endangered themselves. And, Rynax-Kurau, who hadn't departed for this new world, comes back to Christmas.
- Blessed with Suck: Kurau loves her powers, but they cause her quite some grief too.
- Bookends: The first episode has Kurau lonely and desperately wishing for her pair, who finally appears at the end of the episode. The Distant Finale has the same thing happen with the roles switched.
- But Not Too Foreign: Even though it's never outright stated at any point during the series, Kurau is Japanese/Swedish.
- Energy Absorption: Kurau uses it to send other Rynax back to their own world.
- Energy Beings: The Rynax themselves; human research initially thought they were simply energy until they turned out to be alive.
- Gigantic Moon: The full moon looks awfully huge behind the flying silhouettes of Kurau and later Christmas, to make some lovely framing.
- Growing Up Sucks: The disappearance of Kurau's Rynax is a thinly veiled metaphor for the definitive loss of her childhood.
- Holding Back the Phlebotinum: Leading to the unnecessary death of a helpful individual.
- I Did What I Had to Do: Saitou's answer when confronted about his questionable methods.
- Love Hurts: Rynax go through a lot of grief without their pair.
- Luminescent Blush: Especially Kurau in response to Christmas.
- Martial Pacifist: Kurau tries to avoid hurting anyone with her powers.
- Mauve Shirt: Ed fills this role.
- The Men in Black: The GPO hunt down Rynax fused with humans for fear that they're a danger to the world. Or, eventually, to use them as such.
- Parental Abandonment: Kurau and Ayaka. Might be applied to Christmas as well, but her parentage is a bit fuzzy.
- Power Glows: Rynasapiens emit an eerie glow and a high-pitched sound when using their powers.
- Red String of Fate: The bond between two Rynax is the focus of their existences and can only be broken by death.
- So What Do We Do Now?: In the end, Kurau's human half has to deal with being herself again now that her Rynax is gone for good.
- Super Soldiers: GPO under Saitou plans to create controllable Rynax-infused soldiers.
- Tears of Joy: Kurau, at the end of the first episode when Christmas reforms. Despite her gender, it also has overtones of Manly Tears due to how badass and reserved Kurau normally is — the series as a whole is very good at creating powerful emotional moments through quiet understatement.
- The Load: Christmas, until she gains her Rynax powers.
- The Meadow Run: Kurau and Christmas, in the opening credits.
- There Are No Therapists: Despite the fact that Kurau starts acting really weird after the lab incident.
- The Stoic: Inspector Wong has quite the poker face. Also, he wears Stoic Spectacles.
- Vapor Ware: For awhile, it felt like the North American release would fall into this trope. ADV Films licensed it after only a few episodes had aired back in the summer of 2004 (which wasn't common at the time; most shows were licensed months to years after they started). Then months and years went by with no word on a release date. It was finally released in late 2007 and early 2008. This probably contributed to its sleeper status, at least at the sales level. Most of the initial buzz had died off, the fansubs had been in wide circulation, and 4:3 content had begun to fall out of favor when the DVDs finally hit stores.
- Word Salad Title: The "Phantom Memory" part of the title seems entirely meaningless right up until the final episode.