So: Outlet had two "sequels." That's how they were marketed, but in fact they're only related in the vaguest way to the first book. Outlet sold so poorly in English that Vertical decided not to publish the second and third books; which was too bad, but understandable. And of the three, Outlet is by far the best anyway.
The second book was Antenna アンテナ, published in 2001. Looking at how fast the two sequels came out (both in 2001), I think it's pretty clear that the publisher, Gentôsha, was leaning on Taguchi to produce more fiction while the notoriety from Outlet lasted - she was quite the media celebrity there for a while, I understand. The second and third books are in many respects quite close to the first, quite what you'd expect from sequels (except that they don't involve any of the same characters), but they're not nearly as good. They feel rushed, not very carefully crafted, and also like she doesn't really have anything new to say about these themes yet.
And, unfortunately for her, they brought notoriety of quite another kind. Both books brought allegations of plagiarism - detailed exhaustively here. I value my sanity too much to read everything that guy writes, but from what I can tell, he's a troll. That is, it seems like she did research on, among other things, new religions and the Tokyo S&M scene for these books, and certain of her insights come from the books she read and (here's the killer) websites she visited, and she didn't properly note this in her bibliography. I can't see that she stole any sentences, much less paragraphs, so I'm not sure it qualifies as plagiarism for fiction (if she was writing a term paper, it's a different story, kids). But the internets in Japan went apeshit about it, and Gentôsha withdrew the books and issues slightly-revised versions. My read (and I could be wrong) is that, as the first internet-celebrity writer to cross over into the dead-tree world, there was a certain tendency among the 2chan people to see her as a traitor, or a carpetbagger, or something; plus, she's a woman, and trolls love to attack women.
Anyway: Antenna. Overall it’s not as good as Outlet.
It’s kind of following the Outlet formula in reverse. It’s narrated by a male (check) philosophy grad student in his early 20s named Yujiro. When he was 10 his 8 year old sister disappeared from the futon next to his in the middle of the night. Never explained, and it tore the family apart: uncle, living with them, was always suspected, and he killed himself protesting his innocence. Father died next, mother took refuge in crackpot religion. Younger brother – born after sister’s disappearance – is now showing signs of mental illness. Turns out that mother secretly convinced brother (Yuya) that he was really Marie reborn (sister).
Yujiro is once again trying to get to the bottom of the mysterious sibling disappearance (check), and in doing so he’s moving through various scientific, pseudoscientific, and ultimately mystical epistemologies (check). He’s a philosophy major (but this part is never presented very persuasively – no real philosophical name-dropping); his best friend Miki is also one, but she’s really a physiognomist. She recommends he visit a half-Filipina dominatrix named Naomi (check the kinky sex theme), who it turns out is something of a shamaness a la Yuki in Outlet.
Meanwhile, Yuya in his delusions is talking about Marie actually inhabiting his body. And he also raves about having “antenna” – astral antenna, sort of. In the end the mystical worldview of this book isn’t developed as logically or as clearly as in Outlet, but it does involve some kind of astral antenna which are, once again, overlaid with sexual anatomy: yes, Yujiro’s dick is his antenna, and in the end it’s by obsessively masturbating that he manages to access the spiritual/astral realm in which Marie’s spirit, or his family’s disturbed projection of her, is wandering. And he puts her to rest.
Things are much less clear in this novel than in the first one. Marie’s disappearance is never really explained. That is, we’re given repressed-memory evidence that seems sufficient to identify the uncle, but Yujiro doesn’t accept it, so we don’t – and in the end Yujiro’s encounter with Marie’s spirit doesn’t explain why she disappeared, not in a real-world way. Not like Yuki’s brother’s death was explained.
And the mystical underpinnings aren’t as developed as in the first book, either. In the first book she left open the slight possibility that men could become outlets too, that the mystical nature of the universe wasn’t solely open to women – but in the end it was a very feminine vision she was presenting, of a very feminine cosmos. Here she’s developing a male-centered mysticality, redeeming the phallus, but perhaps because she doesn’t want to contradict the vision of the first book, it doesn’t expand into a worldview. How does the antenna fit with the outlet? And, oddly enough, she doesn’t really connect this antenna rhetoric to the tree-antenna imagery in the later parts of Outlet (there it's connected with Findhorn).
On top of that, there’s a theme of delusion running through this book – Yujiro gets from at least two encounters (Yuya’s psychiatrist and Naomi) the idea that beliefs, gestalts, ghosts, mystic perceptions, may all be delusions, and that’s okay: we’re all able to heal ourselves through our own delusions: in fact, that’s what they’re for. Which undercuts a lot of what happens in the end, and may explain why we never get closure on Marie’s death.
Ideologically, that sounds pretty challenging and fascinating. Kind of undercutting the positivism of the first book. But it’s itself undercut by the fact that this is a less powerful fiction: very talky, very repetitive. Too long by about a hundred pages, really.