C (しぃ, Shii), often translated as Shii, is an AA character that debut after the creation of 2channel's /mona/ board in June 2000. She was once considered to be apart of the big four, but has become forgotten over time. In short, she was Giko's lover and lives inside a box.

　　　　　　 ∧_∧　　
　　　　　　 (*ﾟーﾟ) ＿＿＿＿
　　　　 　　 /つ／|　　　　 ／|　
　　　　　～　　 |￣￣￣￣|　.|　
　　　 ､､､､（/　 | ｷﾞｺﾆｬﾝ. |／,,,　　,,

Back then, AA threads were housed on /kitchen/ while Kaomojis had their own /kao/ board. This changed on June 8, 2000 when the /mona/ board was established. Within a few days, a person named “Ｃ”, who later became “Ｃちゃん” (C-chan) before settling on “しー” (Shii), would appear in the Giko threads and made her own character.¹⁾²⁾³⁾ They later adopted a tripcode (◆CgikokqI) and received a capcode (しー★).

Within the next month, her character would be tortured⁴⁾ and a “Genocide Boom” (虐殺ブーム, Gyakusatsu Būmu) sparked on the AA boards from 2002 to 2004, partially as a way to troll people who get invested in these things. The spam would eventually be curbed by mid-2005 and moved to a Shitaraba board, called the "Abnormal Neta Specialty Mona Board" or “Abu Board” (アブ板).

Tsuu (つー) is a Shii variant with Ahya's face, debuting on June 6, 2001 in a fake Shii thread.⁵⁾ The name is obviously a joke about how “shi” (シ) and “tsu” (ツ) looks similar in katakana. In contrast, Tsuu is more active, unpredictable, bratty, and violent, often wielding a knife as a weapon. By the way, Tsuu does not have an explicit gender, but will often be depicted as a flat-chested female tsundere.

　　　　　　　　＿＿∧ ∧
　　　　　　 ／＼　 (*ﾟ∀ﾟ)＼
　　　　　　 ＼／|￣∪∪￣|＼
　　　　 　　　 ＼|＿〓〓＿|

　　　　　　　　＿＿∧ ∧
　　　　　　 ／＼　 (*ﾟ∀ﾟ)＼
　　　　　　 ＼／|￣∪∪￣|＼
　　　　 　　　 ＼|＿つー＿|

　　∧ ∧
　　(*ﾟ∀ﾟ)
　 .（|　　|）
　～| 　 |
　　 Ｕ Ｕ

 　　　　　　∧ ∧　　　三≡　＝|二フ 
　　　　　　 (#ﾟ∀ﾟ)
　　　　　　 / 　つ´　　　　　 　 　 　　三≡　＝|二フ
　　　 　～/　 つ　
　　　　　 (／´　　　　　　　　三≡　＝|二フ

• For those wondering, there are other Shii variants that use other letters of the alphabet, but I'm probably not going to document them all here since it seems like a huge waste of time.
• There have been jokes about Shii being communist as Kazuo Shii has been the chairman of the Japanese Communist Party since 2000, but they're not as common.

• Mona, Giko, and Morala - The other three members from the original big four of 2ch AA.
• Shii's Song - Their most popular Flash animation.

• Shii on the 2ch AA Illustration Project
• Shii on Niconico Encyclopedia