TOMOKO: a lonely and neglected, almost asexual, housewife who gets caught up in a series of erotic encounters, mainly with a far younger female college student causing her sexuality to blossom and take on entirely new aspects.
YUMIKO: a slightly spoiled CEO daughter who is brutally snatched away from her privileged life as a high school student and getting a first-hand experience with the criminal underworld of Tokyo where she meets the yakuza girl Shoko. In the second part of the trilogy, Yumiko has become a young and successful CEO in her own lifestyle company, and she is getting romantically involved with one of her own employees, the charmingly handsome man, Daisuke Nishiyama.
LINDA: a middle-aged Danish high school teacher having a bit of a midlife crisis after her children left the nest, leaving her and her husband to experiment with an open relationship in an attempt to save their failing marriage. In part two she visits Tokyo on a working holiday with the hidden agenda of experiencing the erotic underworld of the megacity firsthand to infuse her life with new passion. Surprising even herself, she gradually falls in love with a Japanese man, and her erotic agenda turns into a classic romance Linda had never dared hope would come her way this side of the grave.
SHOKO: a sexy yakuza girl burdened by a traumatic past but building a lasting friendship with Yumiko despite their initial kidnapper-hostage relationship and widely different social backgrounds. Ambitious and persistent, she starts a slow ascent into the higher echelons of her criminal organization while befriending two young gang members who become her roommates and bedmates.
A unifying theme of the trilogy is the existential crises of its protagonists. Linda and Tomoko, for example, both end up facing momentous choices about what to do with their lives. In addition, there is the coming-of-age theme in that we follow some characters, like Yumiko and Shoko, from adolescence to adulthood.