fukugan 複眼

In Japanese, fukugan 複眼, means "compound eyes," as in insect eyes.

Character: Beel Bub ベル゠ブブ
Anime: Shinchou Yuusha 慎重勇者 (Episode 8, Stitch)

• Meaning
• Examples
• References

Meaning

Literally, fukugan 複眼 means "multiple eyes," or a "plurality of eyes." In English, it's called a "compound eye." Although commonly called "insect eyes," they aren't exclusive to insects—they're found in arthropods in general..

The term comes from the fact such eyes are composed of multiple "ommatidia," kogan 個眼. Each ommatidium is independent, and capable of distinguishing brightness and color.

Basically, it's an eye made out of hundreds of smaller eyes.

The opposite term is tangan 単眼, "single eye," "singular eye," which, in insects, refers to a "simple eye," sometimes called a "pigment pit."

Character: Killa キーラ
Manga: Monster Musume no Iru Nichijou, モンスター娘のいる日常 (Volume 11)

• The design for Killa キーラ, a killer bee monster girl, includes:
• zenshi
  前翅
  Forewing. (of an insect.)
• koushi
  後翅
  Hindwing. (of an insect.)
• shokkaku
  触覚
  Antennae. (not to be confused with ahoge アホ毛.)
• tangan
  単眼
  Simple eyes.
• fukugan
  複眼
  Compound eyes.

In anime and illustrations, tangan 単眼 refers to characters who have one huge eye, e.g. cyclops girls. Consequently, some people use fukugan to refer to:

• Having more than two eyes.
  Also known as tagan 多眼.
• Having more than one iris in a single eye.
  Also known as choudou 重瞳, "polycoria."

According to some people on the internet, the usage above is a mistake—after all, there are already terms for those things—and fukugan should refer only to the following things:

1. Characters with insect-like eyes.
2. Characters whose eyeballs appear to be covered completely with smaller eyes.

That said, there are extremely few illustrations depicting this sort of nightmare fuel (insect eyes), so most of the time fukugan is used it ends up being toward the other sort of nightmare fuel (tagan and polycoria).

Furthermore, someone may see an insectoid character and think their eyes are fukugan just because they're the eyes of an insect character. That isn't always true. Sometimes they're technically tangan. Not that anyone cares, though.

Character: Rachnera Arachnera ラクネラ・アラクネラ
Anime: Monster Musume no Iru Nichijou: Hobo Mainichi ____! Namappoi Douga, 「モンスター娘のいる日常」ほぼ毎日○○！生っぽい動画 (ONA)

• Spiders aren't insects, but they are arthropods. The eyes of a spider aren't compound, though, they're simple eyes.^{[Simple eye in invertebrates - en.wikipedia.org, accessed 2020-02-15]}

Examples

For reference, some examples of fukugan:

項羽

新作ミニ色紙【土蜘蛛】複眼好きや〜笑 #妖怪 #色紙 #蜘蛛 #モノノケ市 #モノノケ市180623 pic.twitter.com/84RByBDaW0

— meRry (@merry_milky) June 22, 2018

In anime, I've yet to find an example of a mostly human character that has insect-like, compound eyes.

All I can find are characters that are insects to begin with.

Besides that, I can find things that are close to fukugan, but aren't exactly fukugan. For example:

• Maniwa Tefutefu 真庭蝶々, from the anime Katanagatari 刀語, is a ninja whose motif is a "butterfly," chouchou 蝶々. He has insect-like eyes, but they aren't exactly compound eyes, they're closer to having four pupils.
• Tommyrod トミーロッド, from the anime Toriko トリコ, canonically has insectoid, fukugan eyes. However, they're just drawn like normal eyes, because the ommatidia are too minuscule to create any sort of visible pattern.

Character: Kochou Shinobu 胡蝶しのぶ
Anime: Kimetsu no Yaiba 鬼滅の刃 (Episode 24)

• Although Shinobu's eye design resembles compound eyes, nothing in the anime indicates those are actually insect eyes.

References

単眼、重瞳、単眼、複眼、多眼
をちょっとまとめてみました。
奇形とか異形の創作している方のお役にたてたら嬉しいです！ pic.twitter.com/uk2MYDGJbA

— 〆蛆憩介。ロッカーごと埋葬 (@Kesukeeee) March 26, 2016

• oddoai
  オッドアイ
  Odd-eye. Heterochromatic eyes.

#毎月18日は多眼の日 というタグを見て初めて知った… 18で「いっぱい」ってこと？

「多眼」と「複眼」は混同しがちだけど、「単眼」も知らない人は「隻眼」と混同してたりするので、まとめてみた。

（あくまで個人の見解であり界隈で一般的かどうか分かりません） pic.twitter.com/5Ybu9X5jR8

— 鮭夫＠ヒトミ先生の保健室⑫1/11発売👁️ (@shakekoujou) June 18, 2017

• sekigan
  隻眼
  Missing one eye.