Sada first comes into contact with Toku's husband Kichi-zo (Tatsuya Fuji) when she takes umbrage at the label of prostitute, though she's already glimpsed Toku administering to Kichi-zo. Pretty soon he becomes a familiar figure, sneaking up and groping Sada while she's vainly trying to scrub the floor. His sexual appetite is legendary and it doesn't matter, to him, that they're both married. Hence, within a short space of time, Sada allows herself to be drawn into Kichi-zo's bedchamber (he is her master after all) where they engage in a bout of frivolous sex. At this instant their increasingly frequent bouts of love-making are free and easy; it's obvious that they connect beautifully (if their delicious orgasms are any guide).
Gradually their relationship intensifies, each of them finding satisfaction only within their gymnastically physical clinches. Kichi-zo finds that he's somewhat jealous of her clients, even though the money they bring in is useful, so he makes an "honest" woman of Sada by marrying her. Now their relationship shifts to one of equals. Whenever Sada wants sex, which is often, she demands it. Occasionally she leads Kichi-zo around by his penis, such is her attachment to his instrument of pleasure. Similarly, Kichi-zo gets the best of both worlds by sleeping with his first wife when he feels like it and returning to Sada at other times. In hindsight, they could have guessed that such a set-up wouldn't work in the long run.
Mention Ai no Corrida in general conversation and the standard riposte is that this is the film where the cast "do it" for real. While this is broadly true, it simultaneously misses the point and nails the movie dead-centre. Throughout Ai no Corrida there is barely a moment when sex of some sort isn't taking place, yet it is thoroughly integrated into the story rather than a gratuitous, exploitative add-on. Sada and Kichi-zo embark on a one-way trip of gratification because they can only hope to escape the harsh constraints of their lives by unleashing their fantasies. The society of the time initially gives the impression of being tolerant and permissive, since individuals can reach the heights of ecstasy in full view of their servants, friends and relatives. However, the reality is exactly the opposite. People are in fact so repressed that they'll barely comment on people having intercourse in front of them, instead pretending that it's just not happening. A vivid example of this is Sada's school-master client -- he adores her attentions but would have to commit suicide if their liaison became public knowledge.
The quality that makes Ai no Corrida unsettling and disturbing is that it straddles the border between actors and lovers. Matsuda and Tonoyama get down to business without the faintest inhibition, engendering the scary thought that the whole film is real (which of course it is). With the artificial safety nets of simulated sex or low-budget porn production standards absent, events feel a little too close to home for comfort. To push the audience down this path, the lovers and the audience are encouraged to match their step; as the latter becomes numbed by the sheer repetition of the sex acts, the former continually raise the stakes. The viewers require ever more shocking situations in order to provoke a response, so sado-masochism and erotic asphyxiation enter the picture. Ironically, when the script dishes up food as a sex tool, the audience recoils in horror.
The performances of Matsuda and Tonoyama are quite extraordinary, though not in the classical, Western sense. As their light-hearted dalliance mutates into something altogether darker, the subtle emotional nuances of the characters shift, adjusting to the new balance. Through actions and imagery, the establishment of Kichi-zo's penis as an object in its own right (with practically a mind of its own) takes place. Sada becomes inseparable from the penis, wishing to hold and caress it, reducing Kichi-zo's status even as the envelope of love tightens around them. Soon there is only space for the two of them (Kichi-zo can no longer have relations with Toku), then just one.
Ai no Corrida is truly unique in its uncompromising portrayal of insatiable lusts, control and obsession. While the characters have sex constantly, continuing to talk, eat and play musical instruments as they do so, the film is both erotic and non-erotic. There is a certain titillation value in the early scenes but by the mid-point of the film, this has all but vanished (though a wry, situational humour remains). However, whichever way you approach Ai no Corrida it's obviously a novel piece of work. The sad thing is that the stigma of making such an open film becomes apparent when you realise that almost no similar films have appeared in over 2 decades.