Ask any Japanese businessman who Shima Kousaku is, and chances are likely they’ll tell you. The protagonist of the long-running Shima Kousaku manga series, he’s a businessman extraordinaire, having risen up the ranks from feisty young employee to veteran CEO—the “Goku” of salaryman manga both for his power and notoriety. One of his other characteristics is his James Bond-esque talent at bedding women, and his escapades have led him to having lovers (and illegitimate children) all over the world, which also led to him and his wife having a divorce.

However, in 2014, after decades of dalliances, 65-year-old Shima Kousaku remarried. The wife: Shima Kumiko (née Oomachi), an on-again, off-again companion who’s about as sexually experienced with the guys as Shima is with the ladies, if not more. While Shima Kousaku is a pretty politically conservative manga overall, it is fascinating to me that his greatest partner is as far from “virginal ideal” as possible. In fact, if there was some sort of contraption to test her sexual “purity,” it would explode into a thousand pieces.

After their marriage, the publisher, Kodansha, released a two-volume Kumiko-only collection titled The Selection of Oomachi Kumiko, which helps provide an overview of their relationship, and it’s an interesting one indeed. There’s also a two-chapter spin-off called JK [High School Girl] Oomachi Kumiko, which showcases her early misadventures and her talent for manipulation.

Kousaku first meets Kumiko in his early days as a section chief at his company. While they’re both talking business at first, Kumiko is quick to present him a gift: hotel keys to her room. There, they make mad, passionate love, and then go their separate ways (as is usual for Kousaku). But then he learns that he’s hardly her only partner in the short term. Kumiko, it turns out, is a sex fiend. Having witnessed her mom have a threesome with two men when Kumiko was 14, her life changed forever into a constant pursuit of carnal pleasure. The only thing is, she tries to keep her true self on the down low, and her boss (who she’s also sleeping with) is realizing something’s amiss. It’s because Shima rocked her world so hard, she couldn’t control her voice that night. Of course.

Eventually, Shima Kousaku is able to solve the problem of her boss, and he only sees Kumiko once in as while, between other lovers. But every time they meet, the sparks fly all over again, and the sex is bigger and better than all else. And it’s of course implied that for every woman Shima has slept with between their lulls, Kumiko’s probably outdone him. This happens repeatedly until both are significantly older and decide to tie the knot. A part of this decision is that Kumiko reveals that she has cancer, which makes Shima realize how much he cares for her (she later gets surgery with his help to remove the tumor).

So in summary, the main romance of Shima Kousaku is as follows: Shima is a businessman who sleeps with women all around the world. He meets Kumiko, who sleeps with men all around the world. They keep doing this (and each other) for around twenty years until deciding, finally, that they like sex with each other best. “Childhood friend” Kumiko is not.

While ultimately Kumiko is rooted in a hyper-sexual, socks-rocking sexpot character type, what I find notable is that she’s still considered Shima Kousaku’s ideal partner even as she ages. By the time she becomes his bride she’s 45 years old, and a series like this whose bread and butter is male power fantasy could easily have the now-elderly Kousaku end up with a young thing in her 20s. The Selection of Oomachi Kumiko books call her Shima’s “everlasting sweetheart” and “eternal companion,” and it kind of works out, as theirs is a world where purity and sanctity take a backseat.