Fold both legs until the knees reach the chest, and the angle of the pelvis shifts a little. On the extension of the missionary, yet the passage of the vaginal canal is set one notch deeper.

Kukkyokui (屈曲位, “flexion position”) is a position in which the receiving side, while supine, flexes both legs deeply toward the belly, draws the knees toward the chest, and tilts the pelvis forward for insertion. Positioned as a derivative of the missionary, it has the anatomical property that, with the alignment of the degree of vaginal-canal flexion and the insertion axis heightened, the tip of the penis more readily reaches the vicinity of the uterine cervix. In the English-speaking world it is sometimes called the flexion position or, colloquially, the mating press. In adult video and adult manga it has acquired a fixed place in the grammar of staging as “the position of deepest insertion.”

Overview

Kukkyokui is performed with the receiving side, on the basis of the supine posture of the missionary, greatly flexing both legs at the hip joints and drawing the knees toward the chest. There are several variants in the position of the knees and the method of holding the legs: a form in which the receiving side embraces their own legs, a form in which the inserting side presses and folds the legs, a form in which both legs rest on the inserting side’s shoulders. The common anatomical feature is the forward tilt of the pelvis (posterior rotation) and the ventral rotation of the vaginal-canal axis.

Whereas the missionary takes face-to-face joining at pelvic neutral as its basis, kukkyokui deliberately creates pelvic forward tilt, thereby shallowly correcting the anterior curve of the vaginal canal and directing the insertion axis toward the cervix. As a result, the penis tip more readily reaches the vaginal fornix (the deepest part of the vagina, the dome-shaped space around the cervix). This “deep reach” is the kinetic core that makes kukkyokui an independent position category.

In love-making guides and sexology literature, kukkyokui is treated under classificatory axes such as “missionary-derived position,” “deep-stimulation position,” and “cervix-stimulation position.” Gentaro Mayama’s Encyclopedia of Sex Education (1997) describes it among a group of applied forms of the missionary, and in modern adult-trade usage the term kukkyokui is used as a technical name, in parallel with colloquialisms such as “manguri-gaeshi” and “mating press” (Japanese tanetsuke-press).

Etymology and names

The word “kukkyokui” derives from the medical-anatomical term kukkyoku (屈曲; English flexion; Latin flexio). Flexion is one of the anatomical terms expressing the direction of joint movement, denoting the movement of bending a joint and reducing the angle between two bones. Hip flexion is defined as the movement of drawing the thigh toward the trunk. The name kukkyokui directly describes the posture in which the receiving side’s hip joints are deeply flexed, a diversion from the medical term.

In the early-modern Japanese forty-eight-hands system (since Hishikawa Moronobu’s Koi no Mutsugoto Shijūhatte, from the 1670s onward), the position corresponding to kukkyokui may have been expressed by names such as “fuka-daki” (deep embrace) or “koi no takinobori” (carp climbing the waterfall), but from the modern period the name “kukkyokui” was standardised along with the penetration of the medical term. citation needed In adult-trade usage, the postwar colloquialism “manguri-gaeshi” (denoting the form in which the receiving side is, literally, turned over by pressing both legs) circulated widely, but this is an extreme variant of kukkyokui and is not completely synonymous with it.

In the English-speaking world, besides flexion position, the colloquialism mating press has circulated widely around adult content as recent internet slang. The word mating press emphasises the posture in which the inserting side applies weight in a form that completely compresses the receiving side, and it took root by way of the English-speaking reception of Japanese anime and adult games.

Anatomical features

Pelvic angle and vaginal-canal axis

The human vaginal canal, at pelvic neutral (standing, ordinary supine), runs at an angle of about 30 degrees forward and upward, with a structure that curves gently forward. The uterus standardly takes a posture of anteversion and anteflexion within the pelvic cavity, and the vaginal fornix forms a dome-shaped space surrounding the front and back of the cervix. When the hip joints are deeply flexed in kukkyokui, the pelvis rotates in the posterior-tilt direction (the direction of lifting the coccyx). This rotation shallows the anterior curve of the vaginal canal and makes the insertion axis a path that heads straight to the deepest part of the vagina. At the same time, because the position of the uterus itself moves slightly upward within the pelvic cavity, the volume arrangement of the vaginal fornix changes, and from the inserting side, the area around the cervix, hard to reach at the shallow stage of joining, comes within range.

Deep reach and cervical stimulation

The “sense of deep reach” in kukkyokui arises from the penis tip reaching the vaginal fornix and the vicinity of the cervix through the above anatomical alignment. On the sensation of the cervix and vaginal fornix, several views coexist in sexology, divided between a position recognising the “cervical orgasm” as an independent orgasm type and a position subsuming it as stimulation of the whole deep vaginal wall. In Atsumi Ishihama’s Dictionary of Sexology (2010), deep stimulation is described not as the cervix alone but as a response of the whole pelvic nerve plexus.

As the subjective experience of the receiving side, expressions such as “a sense of pressure,” “a heavy pleasure,” and “a dull deep sensation” are often reported in love-making guides, distinguished as a sensation different in nature from clitoral stimulation or G-spot stimulation. On the other hand, strong direct stimulation of the cervix may cause discomfort or pain, so the operation of kukkyokui presupposes adjustment of insertion depth according to difference in build, physical condition, and degree of arousal.

Pelvic floor muscles and abdominal pressure

The posture of deeply flexing both legs sustains contraction of the receiving side’s rectus abdominis, oblique muscles, and pelvic floor muscles. This muscular tension has the effect of increasing the tightness of the vaginal canal, while making long maintenance difficult. The tendency of kukkyokui to be operated as a short-duration, concentrated position derives from this constraint of muscular load.

Derivative forms

Deep flexion (knee-chest type)

A form in which both knees are drawn deeply until they cling to the chest and the pelvis is maximally posteriorly tilted. The inserting side covers over, pressing the receiving side’s legs from above. It corresponds to the posture colloquially called “tanetsuke-press” or “manguri-gaeshi” in adult-video staging, creating the deepest insertion axis within kukkyokui. Because it folds the receiving side’s body screen-fold, the inserting side’s weight bears directly on the receiving side’s legs.

Flexion-spread

A form in which both legs are flexed while spread left and right. By making pelvic forward tilt and leg-spread compatible, it achieves exposure of the vaginal opening and deep reach simultaneously. Adding the flexion of the insertion axis to the M-spread posture, it has high visual openness and is one of the basic compositions in adult-video shooting.

Self-held flexion

A form in which the receiving side embraces both legs with their own arms. By entrusting the holding of the legs to the receiving side, the inserting side can use both hands freely, keeping the lead in the joining movement while reaching for the receiving side’s upper body and breasts. A pattern recommended in love-making-guide media as “self-holding flexion.”

Shoulder-carry flexion

A form in which both legs rest on the inserting side’s shoulders and the inserting side leans forward to compress. Corresponding to the both-legs version of the matsubakuzushi, it has high stability of leg-holding by the shoulder-carry. The insertion axis is close to deep flexion, but because there is little trunk rotation of the receiving side, the gaze-crossing of face-to-face joining is easily maintained.

Standing flexion

A form in which the receiving side lies face-up on the edge of a bed or table with the pelvis protruding slightly off the edge, and the inserting side stands and holds both legs. It is easy to align the inserting side’s hip height with the receiving side’s pelvic height, a variant for reproducing the kukkyokui insertion axis in a standing posture. A composition frequently used in adult-video shooting.

Position in the theory of staging in adult video

In the context of adult video, kukkyokui has a fixed function in the grammar of staging as “the position showing the deepest insertion.” In the progression of a scene, the construction in which, starting from the missionary, passing through the cowgirl and the rear-entry, one moves to kukkyokui just before the climax (ejaculation, orgasm), has established itself as one of the standard patterns.

This compositional role of “kukkyokui → climax” is supported by the representational function of visual “deep reach.” The posture of kukkyokui provides a composition that visually emphasises the moment when the inserting side physically overwhelms the receiving side and reaches the deepest part of the joining. The shooting convenience of securing an angle that easily captures a close-up of the vaginal opening and the junction, while keeping the receiving side’s expression, breasts, and trunk in the same frame, also supports the establishment of this staging pattern.

The colloquialism “tanetsuke-press” circulated widely in internet adult content from the 2010s as a word that directly expresses this staging function. The word itself carries a nuance accompanying pregnancy representation, presumed to be a naming by analogy from the compression posture in livestock mating. In the “impregnation-themed” genre of doujinshi and adult manga, kukkyokui is incorporated into the genre formula as a pictorial subject symbolising “the decisive moment of pregnancy’s establishment.”

On the other hand, in women-oriented love-making guides (the sex features of magazines like anan and FRaU, web media like Laundry Box), kukkyokui is often positioned as “an introductory position for deep stimulation.” In the household love-making context, low-load variants such as “embrace both legs” and “put a cushion under the hips” tend to be recommended.

See also

• Cowgirl
• Matsubakuzushi
• Rear-entry
• M-spread
• G-spot