The receiving partner on hands and knees, the entering partner behind. One of the small set of sex positions that recurs across the historical record from the Kamasutra through the medieval Japanese Ishinpo to contemporary clinical sexology, and a foundational element in current Japanese AV staging vocabulary. The pelvic angle the position produces, the visible body-line, and the rhythmic mobility it allows account for its persistence.

Yotsunbai (四つん這い, yotsunbai) is the on-all-fours position, in which the receiving partner is on hands (or elbows) and knees and the entering partner is positioned behind. In Japanese AV staging vocabulary, yotsunbai is the most common form of rear-entry intercourse and one of the yondai taii (four major positions) alongside seijoui (missionary), kijoui (woman-on-top), and sokui (side position). The position is colloquially called bakku in Japanese AV set vocabulary, after the English “back”.

Etymology and definition

Yotsunbai literally means “four-limb crawling” (yotsu, four, plus hai, crawling, with the geminate-n phonological feature). The older written forms yotsuhai and yotsuashi-hai are now uncommon; yotsunbai is the standard form. The English on all fours is the direct anatomical equivalent; doggy style is the colloquial register; rear-entry in clinical writing covers the general category that includes yotsunbai as its primary sub-form.

The narrow sense of the term covers the canonical posture with palms and knees on the surface. The broader sense covers a family of variant postures including elbow-down (hiji-tsuki), high-on-all-fours (with extended arms), and low-on-all-fours (with head down and rear up). The article uses the narrow sense as the default and treats the variants as named sub-forms.

Rear-entry (kouhaii) is the general category covering rear-entry positions; yotsunbai is its principal sub-form. Other rear-entry forms include standing rear-entry (tachi-bakku), sleeping rear-entry (ne-bakku), face-down (fuse-i), rear-entry seated (haimen-zai), and rear-entry-style cowgirl (haimen-kijoui). Yotsunbai is one position within this broader rear-entry family.

Historical record

The position appears in the earliest documented sexological literatures and has been continuously described across cultural traditions.

The Kamasutra (c. 4th century CE) names rear-entry positions after animal postures: kshudraka (small lotus, with the receiving partner on hands and knees), go-yuthika (cow, with deeper torso lowering), and others in this register. The animal-naming convention persists in later South Asian erotic writing.

Chinese fangzhongshu (bedroom-arts) literature, particularly the Suunujing (Plain Girl Classic) attributed to the Later Han period and the later Xuannujing (Mysterious Girl Classic), records rear-entry positions under similar animal-naming conventions, with names including longfan (dragon turn) and huxing (tiger walk). The medieval Japanese Ishinpo (984), compiled by Tanba Yasuyori, draws on these Chinese sources for its sexual-health material in scroll 28 (the Boun-hen chapter), maintaining the animal-naming convention for the rear-entry forms.

In Western sexological writing, the position is treated under the general rubric of rear-entry intercourse from the late nineteenth century onward, with the colloquial English doggy style attested from the 1930s.

In Japanese commercial AV, the term bakku (a phonetic adaptation of English back) consolidated through the 1980s and 1990s as the standard set-floor instruction for yotsunbai. The phrase bakku ikimasu (“going to back-position”) is the canonical direction during shoots.

Anatomical structure

Four anatomical features distinguish yotsunbai from other intercourse positions.

The pelvic angle. With knees on the surface and torso forward, the receiving partner’s pelvis tilts slightly forward, producing an angle that allows deeper penetration than the missionary configuration. This is the structural feature most often cited in clinical writing on rear-entry intercourse.

Hip mobility. The receiving partner’s hips are free to move along the anterior-posterior axis, allowing the receiver to actively contribute to the rhythm of the encounter. The position therefore supports coordinated mutual movement to a greater degree than positions in which the receiver’s hips are pinned.

Visual access. The receiver’s torso line from the back, the hip and buttock line, and the back-of-head and hair are simultaneously visible from the entering partner’s position. In AV staging this visual access is structurally important: the camera frames the line from the rear with the buttock and hip in central position, and the angle reads cinematically.

Breast freedom. The receiver’s torso is unsupported in front and the breasts are free to move with the intercourse rhythm. This is read aesthetically in much commercial AV as part of the position’s appeal.

Staging variants

A set of named variants is standard in current AV vocabulary.

Standard yotsunbai: palms and knees on surface, head up or slightly tilted forward.

Hiji-tsuki (elbow-down): elbows on the surface, head lower, with the back arched and the hips raised. The posture is more demanding for the receiver and is used in shorter-duration sequences.

High yotsunbai: arms fully extended with the upper torso lifted. The posture allows the receiver to face forward and is often used for face-mirror staging.

Kami-tsukami yotsunbai (hair-grasp): the entering partner grasps the receiver’s hair. In AV staging this is often performed gently as a visual element rather than as a forcible pull.

Kagami-mae (mirror-front): the receiver faces a mirror, producing a face-and-action composite shot.

Kousoku yotsunbai (restrained): the receiver’s wrists are restrained at the back and the elbows take the supporting role. Connected to the broader bondage and BDSM staging vocabulary.

Yotsunbai-sokui (side-tipped): the standard yotsunbai with the receiver’s torso tipped sideways, a transitional position between yotsunbai and side-position intercourse.

Yuka-yotsunbai and ofuro-yotsunbai: floor-based (rather than bed-based) and bathroom-based variants, named for the staging surface.

In commercial AV

Yotsunbai (bakku) is one of the yondai taii (four major positions) in commercial AV staging, alongside seijoui, kijoui, and sokui. Nearly all commercial AV titles feature the position somewhere in the running order. The standard structural placement is mid-scene to late-scene, after opening foreplay and the typical missionary opening, with the position transitioning into either standing rear-entry (tachi-bakku) or sleeping rear-entry (ne-bakku) as the scene develops.

The set-floor vocabulary uses bakku or yotsun for the position. The instruction bakku ikimasu moves the performers into the standard yotsunbai configuration; further direction (head down, hips up, elbow down) refines the posture during shooting.

Internationally, doggy style is a top category in major adult-content platforms across all language and regional markets. The position’s combination of strong visual line, anatomical features, and viewer accessibility make it consistently one of the most-viewed categories in adult content.

Cultural associations

The position is recurrently read in cultural commentary as having an “animal” or “submission” connotation, in contrast to the face-to-face configuration of missionary intercourse. The reading is partly built into the colloquial English doggy style and the Kamasutra animal-naming convention. In Japanese AV staging the yotsunbai posture is often used at the moment of the female character’s narrative-climax or “giving in”, with the position itself functioning as a visual marker of the character’s affective state.

Empirical work on position preference (Kinsey 1948 onward, with more recent survey work) has consistently found that yotsunbai and similar rear-entry positions are preferred by a substantial minority of respondents, with reasons including deeper sensation, the absence of face-to-face eye contact (which can read as either an advantage or a disadvantage depending on the respondent), and a sense of releasing inhibition. The respondents who prefer the position tend to have a different preference profile from those who prefer face-to-face positions, consistent with a real preference dimension rather than a continuous-variation pattern.

See also

• Back position
• Ne-back
• Haimen-zai
• Haimen-kijoui
• Kijoui
• Ekiben
• Kannon-biraki
• Uki-chausu
• Mongiri