# Kasane Teto

Kasane Teto (Japanese: 重音テト) is a virtual singer software (known as a voicebank) created on the Japanese textboard 2channel for April Fools' Day, 2008. Although the software was initially created as a hoax and did not exist, it later was actually produced and made compatible with singing voice synthesis software UTAU, allowing it to sing. Teto was introduced as a "diva born from a hoax".
Kasane Teto was also released as a voice model in 2021 for TALQu, a deep learning-based free speech software, and in 2023 for Synthesizer V AI, a commercial singing voice synthesis software.

## Character

Kasane Teto is officially stated to be 31 years old. However, because of the young, girlish appearance and voice that her original UTAU design has, many people have long since interpreted her age to be in her teens. In her earliest design, she was 159.5 centimetres tall and weighed 47 kilograms. She is listed as liking baguettes and being a tsundere.
Kasane Teto’s character design portrays her as a youthful girl with red hair styled in curly pigtails. She typically wears a uniform-style outfit with a red and black color scheme, which has become a recognizable part of her image.
Her personality is portrayed as mischievous.

## History
### Creation

Kasane Teto's origins come from 2channel, a Japanese bulletin board. In 2008, a group of users devised a plan to make a fake Vocaloid character. Character names, hairstyles, genders, ages, likes, dislikes, special skills, and other traits were randomly selected from among the suggestions of 2channel users and consolidated into a single character, which would be shown as a prank for April Fools' Day. On 6 April 2008 she appeared for the first time on video, and on 13 April 2008, the first voicebank for Teto was released, with Oyamano Mayo as the voice provider. The first song using her voice was released on 1 June 2008.
The rights holders who provided the character design and voice of Kasane Teto established the circle "TWINDRILL" in 2009 to promote and manage the character. Although Kasane Teto was a parody character of Crypton Future Media's series of Vocaloid singers, Twindrill organised the rights and established a cooperative relationship with Crypton from 2009 to 2010. Since 2010, Crypton has been the point of contact for commercial use.

### 2010s and 2020s

Teto continued to make an impact on the Vocaloid community with many songs being released. In 2012, a DLC pack for Hatsune Miku: Project Diva F featured her. In 2013, she appeared for Hatsune Miku's act in the Sapporo Snow Festival 2013.

### Synthesizer V

For the 15th anniversary of Teto on 1 April 2023, Japanese software developer AH-Software announced they would be partnering with Twindrill and Crypton Future Media to produce a "Synthesizer V AI" voice database for the character, its first full commercial release. For the occasion, a significant redesign was made, giving Teto a new outfit to stand apart from being a Hatsune Miku parody. The deep learning technology in Synthesizer V made use of singing from the voice provider rather than concatenative phoneme samples like UTAU. This allowed for cleaner, more natural synthesis and various features such as "Vocal Modes" for expression and the ability to sing in any language that Synthesizer V AI supports via "cross-lingual synthesis". Synthesizer V AI Kasane Teto was released on 27 April 2023 and has received frequent updates. A limited "lite" voice database for the same software would come soon after on 8 May 2023, available for free download.

## Reception

Despite not being Vocaloid, Kasane Teto gained popularity among vocaloid fans. Within six months more than 500 videos with "Kasane Teto" tag were published on Niconico, and the song "嘘の歌姫(Uso no utahime/A Fake Diva)" featuring Kasane Teto reached 100,000 views and was put into the Vocaloid Hall of Fame.

### Songs

Some of Kasane Teto's charted songs include:
| Title | Artist | Year | Peak chart positions |
| Title | Artist | Year | JPN Hot |
| "Override" | Yoshida Yasei | 2023 | 75 |
| "Mesmerizer" | Satsuki / 32ki | 2024 | 65 |
| "Tetoris" | Hiiragi Magnetite | 2024 | 35 |

### Other media

Kasane Teto has appeared in multiple media, such as in Sega's music game franchise Hatsune Miku: Project DIVA, becoming a promotional character for Hokkaido Broadcasting, having Nendoroid and other plastic figures from Good Smile Company, performing with Nakamura Shidō II on the Kabuki stage, and having novel adaptations.