This article is also available in Japanese: Read the Japanese version
Have you come across Koseki Bijou? She is active as a member of -Advent-, a unit in hololive English. Her official profile introduces her as “The Jewel of Emotions,” a VTuber formed as the emotions of humankind crystallized over many years. Since her debut stream on July 30, 2023, she has streamed on her own official YouTube channel and, as a member of Advent, has also appeared in 3D projects and concerts.
This article introduces Koseki Bijou's profile and activities based on hololive's official talent page, COVER Corporation's official news, the official event page, and the official shop. This article does not use guesswork to fill in private matters that the official side has not made public, such as her real name, real age, hometown, family, or her so-called past identity or the person behind the character.
Koseki Bijou's Official Profile: Birthday April 14, Height, and Debut Date
Name: Koseki Bijou
Name in Japanese: 古石ビジュー
Birthday: April 14
Debut Stream: July 30, 2023
Height: 140 cm
Unit: hololive -Advent-
Illustrator: Kitada mo
Affiliation: hololive English
The official hololive talent page collects details such as her birthday, height, and debut date. The birthday and height listed there come from the official profile published for her as a VTuber.
Her illustrator is Kitada mo. So as not to confuse the talent's own activities with the person responsible for the character design, this article follows the official page and treats the two separately.
Her debut stream is recorded as July 30, 2023. When checking milestones in her career, the safest starting point is probably the official talent page, not clips or roundup sites.
“The Jewel of Emotions” Is Her Official Character Lore
The official profile presents Koseki Bijou as “The Jewel of Emotions.” In the lore, she is a being formed when humanity's many emotions, the beautiful and the filthy alike, crystallized under immense pressure over many years. The profile also explains that conflict broke out over her brilliance, so she was imprisoned in secrecy, far from the reach of humans.
This is a character story published by hololive. It does not describe her real-world background, personality, or hometown. Enjoying the lore as lore, while checking her actual track record through official news and her own official channel, may make it easier to sort out and follow what makes Koseki Bijou appealing.
The official page also lists her videos and music. That same page shows that her activities reach beyond the profile story into streaming, music, and 3D appearances.
Active as a Member of hololive English -Advent-
Koseki Bijou's unit is hololive English -Advent-. Advent also includes Shiori Novella, Nerissa Ravencroft, Fuwawa Abyssgard, and Mococo Abyssgard. Both the official talent list and the 3D Showcase announcement place Koseki Bijou alongside these same members as part of Advent.
Streams on her personal channel and activities under the Advent name are not the same thing. Checking her official YouTube channel for solo streams and hololive's official news for unit projects makes the two easy to tell apart.
The music section of the official page also lists Advent songs. Titles and where they are available may be updated after release, so the official music pages are the safe place to check for the latest information.
Her Individual 3D Showcase in 2024
On July 12, 2024, COVER Corporation officially announced the 3D Showcase schedule for the Advent members. The official 3D Showcase announcement lists Koseki Bijou's showcase as starting at 8:00 p.m. PDT on August 3, 2024. That is noon JST on August 4, 2024. The announcement also listed her official YouTube channel and the hashtag #Biboo3D.
The same announcement also included a 3D collaboration stream featuring all of Advent. Because the individual 3D Showcases and the unit's joint stream were scheduled on separate dates, you can check Koseki Bijou's own appearance without mixing it up with the Advent-wide project. The stream took place on her channel on August 4, 2024 (JST), and the archive is available.
Performing at the 2026 hololive English 4th Concert
On July 3 and 4, 2026 (local time), the hololive English 4th Concert -Serendipity- was held in Los Angeles. Koseki Bijou's name appears in the cast list on the official event page. The venue was the Shrine Auditorium, and the concert was organized by COVER Corporation.
The official concert report records her performance in a unit with Takanashi Kiara, as well as her singing with IRyS and Ookami Mio. It is striking that the official record includes not only her Advent stages but also stages she shared with members of other units and with guests. Song titles and performer pairings can be confirmed from the official event page's record, without relying on fans' memories alone.
The path from her own 3D Showcase in 2024 to the 2026 hololive English concert probably makes it easy to see that her 3D activities have continued.
2026: A Birthday Project and an Overseas Collaboration
The hololive production official shop has a product page for “Koseki Bijou Birthday 2026.” The page presented merchandise and digital content as a project celebrating the birthday of Koseki Bijou from hololive English. The page states that the order period ran from 1:00 p.m. on April 15 to 6:00 p.m. on May 18, 2026 (JST). The order period has already ended. The shop notes that voice packs may continue to be sold after the period, but sales may end without notice, so if you are thinking of buying, please check the official shop.
In addition, in its official news on the “Dive into hololive cafe”, COVER Corporation announced Koseki Bijou as one of four talents appearing in a new key visual. This collaboration ran from February 27 to April 26, 2026, at the National Museum of Marine Science and Technology (NMMST) in Taiwan and at a cafe in Taipei.
The birthday project and the overseas collaboration are different in nature, but both are official records from 2026 and offer clues to her current activities.
Follow Her Own Activities on Her Official YouTube Channel
Koseki Bijou's official YouTube channel is also linked from her hololive talent page. As of September 26, 2026, the channel name is “Koseki Bijou Ch. hololive.” To follow her streams and videos, it is best to start from this official channel rather than compilation videos or reuploads.
As of September 26, 2026, her YouTube channel had 996,000 subscribers and about 140.49 million total views. Subscriber and view counts change every day, so please check the official channel for the latest figures.
Koseki Bijou: A VTuber Whose 3D and Music Activities You Can Follow Through Official Records
Koseki Bijou is a VTuber in hololive English -Advent-. Her official profile lists her birthday as April 14, her debut stream as July 30, 2023, and her height as 140 cm. Her individual 3D Showcase took place in 2024, and in 2026 she performed at the hololive English 4th Concert -Serendipity-. Also in 2026, a birthday project and an overseas collaboration were rolled out officially.
Putting together several primary sources (her profile, the 3D Showcase, the concert, the official shop, and the overseas project) lets you see concretely how far her activities have spread. If you're starting to follow her now, the official talent page and her official YouTube channel are the surest places to begin. You can learn plenty about Koseki Bijou's activities from official sources without guessing at undisclosed information such as her real name, real age, hometown, or family.
