What is Cirno's Perfect Math Class?

It is a 2008 IOSYS doujin song and flash music video that remixes Cirno's Touhou boss theme Beloved Tomboyish Girl into a bouncy math-class skit full of ice-fairy in-jokes.

Where did Cirno's Perfect Math Class come from?

IOSYS members ARM and Yoshimi Tano wrote and arranged the song, miko sang it, and TETLA POT animated the video, which went up on the album's promo site on October 25th, 2008.

What does Cirno's Perfect Math Class mean?

The joke is that Cirno, famously labelled '9. Moron' in Phantasmagoria of Flower View, is somehow running the classroom, hence the recurring nine-ball (⑨) imagery and shouts of 'baka' in the chorus.

How do you use Cirno's Perfect Math Class?

Fans typically repurpose the song as a MAD backing track, swapping in characters like Angry German Kid or Shuzo Matsuoka, or performing the Odottemita dance cover at Touhou meetups.

Is Cirno's Perfect Math Class still popular?

It is a classic Touhou meme; Niconico's song tag listed over 3,600 related uploads by 2014, and IOSYS kept the format alive with a 2010 Phys-Ed themed sequel at Comiket 78.

$Cirno's Perfect Math Class — Cirno smiling with closed eyes beside an answer box reading '0人'$

Cirno's Perfect Math Class

2008music video / doujin songclassic

Published October 8, 2026

Cirno's Perfect Math Class is a 2008 Touhou Project arrangement by the doujin circle IOSYS, pairing a bouncy remix of Cirno's boss theme with a flash music video full of ice-fairy in-jokes. The song exploded on Nico Nico Douga within days of release and spawned one of the defining Touhou memes of the late 2000s, from Angry German Kid MADs to prefecture-level flash mob dances.

japanese internet memes nico nico douga memes otaku culture memes earworm memes flash animation memes

Overview

Cirno's Perfect Math Class (チルノのパーフェクトさんすう教室, Chiruno no Pāfekuto Sansū Kyōshitsu) is an IOSYS arrangement of Cirno's Embodiment of Scarlet Devil boss theme Beloved Tomboyish Girl, framed as a bubbly song about the ice fairy teaching arithmetic she can barely do herself1. The joke runs on Cirno's long-standing fan reputation as a lovable idiot, cemented by the Phantasmagoria of Flower View manual listing her as '9. Moron,' which is why nine-ball graphics (⑨) and the word 'baka' plaster the chorus2.

TETLA POT's flash music video stuffs the frame with Touhou in-jokes and Japanese pop culture gags, including the Columbia Pose and the Kira Pose during instrumental breaks2. The format that followed on Niconico fed off the song's extreme earworm quality and short, hookable chorus, which made it ideal source material for MAD video edits swapping the vocals or visuals with unrelated characters2.

The song is also widely performed as a dance in the Odottemita (I tried dancing) scene, with choreography that fans picked up and reused at Touhou meetups and conventions across Japan2. IOSYS later built on the format with a Phys-Ed themed sequel, keeping Cirno in the subject-teacher role2.

Gallery

Origin & Background

Platform

Hyosetsukashu album site / Nico Nico Douga (viral spread)

Key People

IOSYS with animation by TETLA POT

Date

2008

The track was written and arranged by IOSYS members ARM and Yoshimi Tano and sung by miko, released on the circle's album Touhou Anthology of Ice and Snow (東方氷雪歌集) at the Touhou Kouroumu 4 convention on November 2nd, 20082. To promote the album, IOSYS put the song online a week early with a flash-animated music video by TETLA POT, posted to the album's since-defunct Hyosetsukashu site on October 25th, 20083. The source composition is ZUN's Beloved Tomboyish Girl (おてんば恋娘), the Stage 2 boss theme for Cirno in Embodiment of Scarlet Devil2.

The math-teacher premise did not come out of nowhere. Cirno's dim-wit characterization had been a Touhou fan staple since Phantasmagoria of Flower View in June 2005, and Chibitami had already made a browser flash game called Math Brain Training to become ⑨ Cirno in June 2008, where the player wins by answering every math question with 94.

How It Spread

The music video jumped to Nico Nico Douga on the day of its web release, where it pulled over a million views in roughly two weeks5. The full-length version leaked to the site on October 31st, 2008 and went on to clear 1.2 million views on that single upload6. IOSYS was already a Niconico powerhouse, which fueled a wave of MAD video edits almost immediately, including an early Angry German Kid mashup posted on November 4th, 20081.

The mashup that broke out hardest was a Shuzo Matsuoka version uploaded November 5th, 2008, which crossed 1.5 million views7. Dance covers followed four days later, kicked off by Niconico dancers Kyōfu. (恐怖。) and kuu. on November 9th, 2008, a video that pulled around 1.4 million views and seeded regional dance meetups across Japanese prefectures1.

By July 2014, Niconico's tag for the song listed more than 3,600 related videos, with YouTube reuploads mirroring much of that catalog8. IOSYS extended the gag with Cirno's Perfect Health And Physical Education (チルノのパーフェクトほけんたいいく) on their Touhou Love Strawberry Girl+ album at Comiket 78 on August 14th, 20101.

Timeline

2005-06

Cirno is listed as '9. Moron' in the Phantasmagoria of Flower View manual, fixing her fan reputation as a dim-witted ice fairy[1].

2010-08-14

IOSYS releases the follow-up Cirno's Perfect Health And Physical Education on Touhou Love Strawberry Girl+ at Comiket 78[1].

2014-07

Niconico's song tag passes 3,600 related video uploads[8].

How to Use This Meme

Fan remixes typically keep the chorus hook intact and swap in a new vocal, visual, or character over the flash video's structure. Common conventions include splicing in another loud or iconic clip (Angry German Kid freakouts, Shuzo Matsuoka pep talks) and syncing it to the song's beat, or performing the official-style dance choreography in groups at Touhou events5.