The company was founded in 1959 as a magazine advertising agency. Its history between then and the late 1980s is generally unknown, but the company began reorganizing into an animation business called Studio Kikan (スタジオ旗艦) around 1989. Sources disagree on the exact foundation date as a rebranded animation studio. Despite starting reorganization in 1989, sources differ on the company's official date of rebranding. The company was first credited in 1993 and the Association of Japanese Animations listed the studio's foundation date in April 1993, while the company began unofficial animation activities as early as 1992 and the National Corporation Directory claims Studio Kikan's foundation date as October 1992. The new animation business was established by ex-Hero Communications and ex-Urban Product producer Keiji Kusano—who served as the company's first president and CEO—and producer Yoshikazu Tochihira, formerly of the short-lived Animation 21[ja]. The studio was physically based out of the Animation 21 office in Nerima. Director Kiyomu Fukuda and the staff of his Atelier Fukurou studio, including animators Rin Shin and Tatsuya Kawashima, also joined the company.
The company initially took on production of various OVAs, including hentai works. Studio MTV originally intended to produce La Blue Girl with director Kinji Yoshimoto in 1992, but the company closed from bankruptcy during production of the first episode, and he was not involved with the direction at all. Studio Kikan then took over production as its first unofficial work (episode 2) and official work (episodes 3 and 4). The initial production period was also difficult as much of the work was subcontracted overseas. Fukuda, directing under the penname Kan Fukumoto (ふくもとかん), and Rin-Sin visited South Korea where much of the animation was being outsourced to. According to Fukuda, much of the key animation was rejected and had to be redone from scratch, while Rin-Sin was doing her first job as both animation director and character designer. According to Osamu Shimizu, another ex-Hero Communications producer who joined Studio Kikan, the cel-photography stage of the animation was produced in Korea, as well.
The studio's first television series also debuted that year as the long running Shima Shima Tora no Shimajirō, which was originally meant to be produced at Animation 21 before it closed down due to financial issues. With the exception of Lady Blue, a sequel to La Blue Girl, the company started using the brand names Dandelion (ダンディライオン) and Triple X for hentai OVA productions. In 1996, Arms was founded as a separate production label and studio to take over Studio Kikan's hentai business, with Shimizu as the head of the company. Despite the separation of the entities as separate studios, the two companies worked with the same producers and animation staff.
Starting around 1995, the majority of productions and episodes outsourced from other studios either went under the Dandelion and Triple X labels, or were credited to Arms itself. Another label, Garyuu Studio (呀龍スタジオ), was also briefly used between 1999 and 2005. The two companies started taking on outsourcing work from Studio Pierrot that year, with episodes of Microman (1999), Great Teacher Onizuka (1999), and Tokyo Mew Mew (2000) being outsourced to the Garyuu Studio label. In 2002, the Garyuu Studio label was used to co-produce From I"s under Pierrot, which eventually led to Arms taking on full animation production responsibility for I"s Pure under Pierrot's production in 2005. Producer Osamu Koshinaka commented on the decline of hentai works into the 2000s, and Arms eventually switched fully to TV animation production in 2005.
A decade after first starting the relationship that extended into producing episodes of Naruto (2002–2017) and Bleach (2004–2012), Studio Kikan became a subsidiary of Pierrot and changed its name to Pierrot Plus (ぴえろプラス), sometimes written as Pierrot+, in 2009. Kusano retired as CEO of the company but was retained as chairman of the board with Shimizu replacing him, thereby becoming CEO of both the renamed Pierrot Plus and Arms concurrently. With the Pierrot Plus rebranding, the two companies simultaneously produced television works under their name until around 2015 when Arms as a production house seemingly ceased operations. Arms changed its trade name to Common Sense (株式会社コモンセンス) in 2017 but maintained the Arms label as a trade name, and the company's final product, Ikki Tousen: Western Wolves, was released in 2019. By then, most of the staff had already reorganized entirely under Pierrot Plus, and Pierrot was subcontracting entire series like Tsukiuta The Animation (2016) and Tokyo Ghoul:re (2018) to the studio.
On September 20, 2019, the company changed its name again to Studio Signpost (stylized as St. Signpost). Ken Hagino, a prominent producer at Pierrot since the 1990s, was appointed as the new CEO, with Kusano retiring as chairman and Shimizu taking a position on the board. The following year, Arms was dissolved and liquidated following a shareholder meeting, though Studio Signpost continues to use Arms as a brand name for works like Shin Ikki Tousen as of 2022. In 2026, Hagino was made chairman and co-CEO of the company with former Pierrot producer Naoyuki Oshikiri taking the role of president and co-CEO.
Series in which Studio Signpost, Pierrot Plus, or Studio Kikan served as a gross (full) outsourcing studio, either for singular episodes or across entire series.
Keiji Kusano (co-founder, president of Studio Kikan (1992~2009))
Yoshikazu Tochihira (co-founder and animation producer, 1992~2008)
Osamu Shimizu (Studio Kikan producer (1992~2009), president of Arms (1996~2020, president of Pierrot+ (2009~2019), board member of St. Signpost (2019~present))
Ken Hagino (president of Studio Signpost (2019~present))
Animation producers
Shintarou Nozaki (1994~present, also a part of Arms)
↑Although episodes 3 through 6 are credited to Studio Kikan, the interview broadly refers to it as the product of Arms.
↑Although Arms is credited with the animation production of Shin Ikki Tousen, the company declared bankruptcy in 2020, and Studio Signpost used "Arms" as a brand name for production of the work.
↑From Studio Marine, which did gross outsourcing work on the OVA.
