W Sitting (Sitting on Floor Forming a W Shape with Your Legs, ぺたん座り)

In anime, when a character sits on the floor with their butt between their legs, forming a W shape, this is called "W-sitting," daburu-zuwari Ｗ座り, petan-zuwari ぺたん座り, petanko-zuwari ぺたんこ座り, wariza 割座, onnanoko-zuwari 女の子座り, or ahiru-zuwari アヒル座り.

Character: Amamiya Elena 天宮えれな
Anime: Star☆Twinkle Precure, スター☆トゥインクルプリキュア (Episode 10)

• In Japanese
• Causes
• Examples
• References

In Japanese

There are way too many ways to say "W sitting" in Japanese. The most common one would be:

• onnanoko-zuwari
  女の子座り
  Girl sitting.
  • It's said that only girls sit this way, to the point that some people think boys physically can't sit like this.
  • This term sometimes refers another way to sit called yokozuwari 横座り.

Some other terms:

• wariza
  割座
  Parted sitting.
  • Because it's one foot to each side, I guess
  • waru
    割る
    To part. To divide.
• petan-zuwari
  ぺたん座り
  Contact sitting.
  • Because the butt is making contact with the floor.
  • petan
    ペタン
    To make contact with a flat surface.
    (mimetic word.)
• ahiru-zuwari
  アヒル座り
  Duck sitting.
• Because ducks, too, sit like this.
• daburu-zuwari
  Ｗ（ダブル）座り
  W sitting.
  • daburu is the katakanization of the alphabet letter "W."
• obaachan-zuwari
  おばあちゃん座り
  Grandma sitting.

Someone out there probably calls it "M sitting" instead of "W sitting," as that's a matter of perspective.

Character: Yuzuriha Maimai 楪舞々
Anime: Zombieland Saga: Revenge (Episode 7)

• POV: you are a cute anime girl.

Causes

W sitting is the preferred way to sit by many young children because they have a degree of femoral anteversion (how much the leg is rotated is relation to the hip) that makes it more comfortable to sit in this position. By 8–10 years old, their hips "unwind," and they stop W sitting.^{(westernkidshealth.com)}

W sitting is a cause of worry in parents that believe it's harmful, although research says it doesn't affect the shape of the hip bone, doesn't cause hip displasia, degenerative joint disease, arthritis, or in-toeing, and there's no evidence it causes motor delays or core weakness.^{(westernkidshealth.com)}

At least that's how it is in the west, referring to developing children.

In Japan, things are a bit different because of the custom of sitting on the floor.

The proper way to sit on the floor is called seiza 正座, in which you sit on your legs, but some people may find this position uncomfortable and prefer W sitting.

Left: Minami Kana 南夏奈
Right: Minami Chiaki 南千秋
Anime: Minami-ke みなみけ (Episode 9)

• Context: sisters have a conversation next to a zataku 座卓, a table low in height that you use while sitting on the floor.

Examples

There's an article on TVTropes called Twisted-Knee Collapse about this way to sit, due to girls ending up in this sitting position when they fall on the ground.

Character: Kinomoto Sakura 木之本さくら
Anime: Cardcaptor Sakura, カードキャプターさくら (Episode 1)

• Context: relieved after winning her first battle as a magical girl, Sakura collapses W sitting on the floor.

It typically shows up in moe 萌え anime because it's considered cute.

Character: Sasha Necron サーシャ・ネクロン
Anime: Maou Gakuin no Futekigousha: Shijou Saikyou no Maou no Shiso, Tensei shite Shison-tachi no Gakkou e 魔王学院の不適合者 ～史上最強の魔王の始祖、転生して子孫たちの学校へ通う～ (Episode 2)

• Context: upon being defeated, Sasha falls on the ground making a perfect W.

Character: Usami Masamune 宇佐美マサムネ
Anime: Mayo Chiki! まよチキ！ (Episode 5)

• Context: a traffic accident leaves its zettai-ryouiki 絶対領域 donning perpetrator W sitting.

Character: Maaka Karin 真紅果林
Anime: Karin かりん (Episode 1)

• Context: a reverse vampire nosebleeds so hard she ends up W sitting on the floor.
• kyuuketsuki
  吸血鬼
  Suck-blood-demon.
  Blood-sucking demon.
  Vampire.
• souketsuki
  増血鬼
  Increase-blood-demon.
  Blood-increasing demon.
  What Karin calls herself.
  • fueru
    増える
    To increase.

Left: Cthuko クー子
Right: Shantak-kun シャンタッ君
Anime: Haiyore! Nyaruko-san 這いよれ！ニャル子さん (Episode 3)

• Context: an eldritch abomination drawn as a cute anime girl W sitting.

As mentioned in the name onnanoko-zuwari, this way to sit is associated with girls, so male characters are rarely shown sitting this way, except for otokonoko 男の娘, "trap," characters.

Character: Urushibara Ruka 漆原るか
Anime: Steins;Gate 0 (Special, Stitch)

• Context: Ruka crossdressing with kemomimi ケモミミ as a fox girl

Character: Ayasaki Hayate 綾崎ハヤテ
Anime: Hayate no Gotoku! ハヤテのごとく！ (Episode 8, Stitch)

• Context: Hayate crossdressing with nekomimi 猫耳 as a cat girl.

Conversely, a way to sit on the floor that's typically used by boys and not girls would be "cross legged," in agura あぐら position.

References

• W Sitting - why the drama? - westernkidshealth.com, accessed 2021-04-2021.