Koushirou Saeki is a wedding planner, but that's just his job. In his personal life, he's a taciturn lump with a troubled family background and a natural disinclination to get involved emotionally with people. On a bad day he can come across as sullen or even hostile. Unsurprisingly his girlfriend is about to dump him. He lives with his immature father and he hasn't seen his mother or sister for twelve years. He probably wouldn't even recognise the latter if they met in the street.

Koi Kaze is a "boy meets girl" story with a difference. Forget the fact that he's twenty-seven and she's a schoolgirl of fifteen. That's nothing in anime. No, you need one more shattered taboo for that authentic Japanese experience and this one's a doozy. The moment I read the reviews, this show had to be watched.

She's his kid sister.

Koi Kaze is the latest show from the makers of Serial Experiments Lain, Haibane Renmei and Texhnolyze, so we know it's going to be thoughtful, subtle, delicate and probably very slow. This isn't the work of some sleazy fly-by-night studio with money to burn and a complete taste bypass... which is arguably a shame, since that would have probably been a lot of laughs.

However Koi Kaze has integrity. It doesn't cheat by casting beautiful people as the leads and shrouding their actions in fluffy cuteness. He's slightly ugly, a couple of stone overweight and older-looking than his years. She's round-faced and vaguely pretty, but in a little sister kinda way. When they're side by side, she looks twelve.

Similarly their world is far from glamorous. Koushirou's work isn't romantic, but just another office job. His girlfriend dumps him in episode one because she's not getting enough out of their relationship. The animation is unremarkable and the voice acting is deliberately understated, with Koushirou mumbling in a semi-monotone and Nanoka sounding so calm and controlled that her performance occasionally seems to contradict the visuals. Despite its explosive subject matter, this show could hardly be less sensationalist.

Personally I really liked it. The slow pace worked better than in Serial Experiments Lain and Haibane Renmei, which for me got a bit boring. Love stories are about character rather than plot. Thus one doesn't mind quiet scenes that don't go anywhere, since you're watching the subtext rather than the text. What's more, it's funny! The tone is serious drama rather than comedy, but despite this it's full of little character moments that made me chuckle.

It mostly manages not to be creepy. We know our heroes too well for that. Koushirou is doing his cloddish best to suppress his feelings and do the right thing, although unfortunately this makes him overcompensate and become gruff and aggressive. Paradoxically this makes him more interesting as a romantic lead, making his gentler scenes more meaningful. Eventually, almost despite themselves, the two of them are charming. If you can stop boggling at the "schoolgirl incest" angle, then this is a story of two people who love each other but know that they shouldn't. Stories are always more moving when the heroes have to overcome obstacles and that's certainly true here. There are a thousand reasons why Koushirou and Nanoka shouldn't go near each other and in their own ways they're both killing themselves trying to do the right thing in an impossible situation.

I wouldn't dream of giving away the ending, which could have gone in all kinds of directions. In particular the final episode is almost scary, continuing the story beyond one possible point of conclusion and keeping one nervously wondering what's about to happen. I particularly enjoyed the other characters' reactions. One best friend discovers the truth and confronts Nanoka, while another best friend merely suspects...

Fascinatingly episode eight was omitted from the original Japanese TV run as too controversial, since it's a flashback to when Nanoka and Koushirou's parents got divorced. Japan, eh? Divorce is taboo, but incest is fun for all the family. In fact that's a really important episode, since it adds a whole new perspective to see them together when they were children. Oddly enough Nanoka even as a cute toddler was mesmerised by her big brother and upset by his stand-off-ishness. You'll also be pleased to know that Nanoka turns sixteen during the show. This may not mollify Americans but eighteen isn't the only age of consent in the world, although I'm not aware of any age of consent for banging your brother.

This show will mess with a lot of people's heads. It's a serious-minded plunge into deep deep waters, with a script and production that keeps dangerous subject matter on the tightest of reins. It's also based on a real psychological phenomenon: genetic sexual attraction. Blood relatives really do tend to be attracted to each other, but there's also something called the Westermarck effect in which close proximity during childhood will prevent sexual feelings towards that person. Koi Kaze is an impressive piece of work and often sufficiently gripping that it's hard not to watch the next episode. Quite an achievement!