A-set

A-set, real name Iris Sagan (左岸 イリス, Sagan Irisu), is a female Japanese and English Virtual YouTuber who was created by Kozaki Yūsuke and Uchikoshi Kotaro for the Japanese video game developer Spike Chunsoft. She is one of the main characters of the Spike Chunsoft game AI: The Somnium Files. In-universe, she belongs to the idol agency Lemniscate.

Her presence on YouTube and social media began as part of a Viral Marketing Campaign to promote AI: The Somnium Files. She also occasionally makes tweets and videos about other Spike Chunsoft games, and comments on gaming news in general.

On July 2019, she went into semi-retirement. With two bonus videos being uploaded post-release.

Both the Western and Japanese accounts still actively tweet, though the latter has stopped making original tweets entirely as of September 19th 2020, and only retweets fan art of the game alongside promotional tweets from the main Spike Chunsoft account.

Personality
A-set is a cheerful and optimistic girl who approaches life with enthusiasm. She began dancing at an early age, and later in her childhood picked up interests in gaming, movies, Egyptian mythology, and the occult. She maintains an interest in urban legends and unsolved mysteries, occasionally discussing these topics on YouTube and social media.

She has a strong relationship with her mother Hitomi, who she considers the most important person in her life. Her best friends are Okiura Mizuki (沖浦 みずき) and Matsushita Ota (真津下 応太). Ota considers himself one of her biggest fans and interacts with her via his own Twitter account.

Trivia

 * She is a fan of various real-world media properties, including JoJo's Bizarre Adventure, Danganronpa, Pokémon, Super Smash Bros., and Steins;Gate. She also frequently expresses her love for the fictional game ShovelForge.
 * An official LINE sticker pack (Japanese) is available featuring her.
 * Her single, Invincible Rainbow Arrow, debuted with her in her first YouTube video. The full version was later made available on the album "AI: THE SOMNIUM FILES Complete Soundtrack -RaiNBOW AFFaiR-".
 * The actual Somnium Files game contains numerous inconsistencies with the events depicted in the videos alongside the accounts, most notably with her description of Naixatloz. Seemingly due to the decision of turning her a Vtuber happening very late in development.

Media

 * Japan Lemniscate - Japanese YouTube channel
 * Lemniscate English - English YouTube channel
 * @a_set_on - Twitter account (Japanese)
 * @Lemniscate_Aset - Twitter account (English)
 * aseton - Official Weibo account

Further readings

 * Iris Sagan - AI: The Somnium Files wiki (contains spoilers)