3 Mouth

In anime, sometimes a character's "mouth becomes a 3," kuchi ga san ni naru 口が３になる.

Like this: ・3・.

Not like this: ・ω・. See nekoguchi 猫口 for mouths drawn like 3's rotated.

Character: Kuga Yuuma 空閑遊真
Anime: World Trigger, ワールドトリガー (Episode 2)

• Meaning
• Examples
  
  • Pouting
  • Blowing Air
• References

Meaning

Mouths are drawn like 3's for various reasons.

1. The character is pouting.
   • kuchi wo togarasu
     口を尖らす
     To pout.
2. The character is trying to kiss somebody.
   • kisu wo semaru
     キスを迫る
     To urge [someone] to kiss.
   • kisu-machi
     キス待ち
     Waiting for a kiss.
3. The character is whistling, or blowing air.
   • kuchibue
     口笛
     Whistling.

And so on.

There are also cases where a character's mouth is simply drawn like a 3 as part of their design, or the author just keeps drawing mouths like 3's for no reason at all.

Most of the time, however, it's going to be pouting, or something similar to pouting, used, mostly, like this:

• But I thought it was a great idea.
• But I don't want to do that.
• But it would look great on you.

In other words: they're mostly drawn when characters without common sense get their nonsense dismissed or questioned by more serious characters.

Examples

For reference, some examples of characters with 3-shaped mouths.

Pouting

Left: Hiiragi Kagami 柊かがみ
Right: Izumi Konata 泉こなた
Anime: Lucky☆Star, らき☆すた (Episode 4)

Left: Nano ナノ
Right: and Mile マイル
Anime: Watashi, Nouryoku wa Heikinchi de tte Itta yo ne! 私、能力は平均値でって言ったよね！ (Episode 7)

Character: Kuga Yuuma 空閑遊真
Anime: World Trigger, ワールドトリガー (Episode 16)

• See also: 3-shaped eyes.

Character: Excel エクセル
Anime: Excel♥Saga, エクセル♥サーガ (Episode 4)

Blowing Air

Left: Shikada Kokonotsu 鹿田ココノツ
Right: Shidare Hotaru 枝垂ほたる
Anime: Dagashikashi だがしかし (Episode 1)

• Context: Hotaru ate something spicy.

Character: Tenma Gabriel White 天真=ガヴリール=ホワイト
Anime: Gabriel DropOut, ガヴリールドロップアウト (Episode 3)

• Context: musical notes symbolizing whistling.
  

Character: Hasuta ハス太
Anime: Haiyore! Nyaruko-san 這いよれ！ニャル子さん (Episode 7)

• Context: Hasuta's soul comes out of his mouth. As far as anime is concerned, a soul is a gas like air.

References

• 口が3 - dic.pixiv.net, accessed 2020-02-23.