|Industry||Video game industry|
|Founded||1 September 1995
5 September 2013
(As Sega Dream Corporation)
1 April 2014
(Established as a new company after separation from Atlus)
|Headquarters||Taishidō, Setagaya, Tokyo, Japan|
|Hideki Okamura (Representative Director and Chairman)
Yasuhiko Hamada (President & CEO)
|Owner||Sega Sammy Holdings|
Number of employees
|166 (April 2014)|
|Parent||Sega Games Co., Ltd.(2013–present)|
Index Corporation was originally founded on 1 September 1995, as a mobile content service provider and expanded into one of Japan's most successful companies, with acquisitions into several communications and entertainment ventures, including the anime studio Madhouse, game companies Atlus and Interchannel, and major movie studio Nikkatsu. It also made inroads into numerous worldwide ventures, including the United States, United Kingdom and France, where it owned the football club Grenoble Foot 38, which, upon Index's acquisition, achieved promotion to Ligue 1. Up to 2013, Index Corporation had sold most of its subsidiaries. In June 2013, following investigations for fraud, Index Corporation was forced to file for civil rehabilitation bankruptcy.
On November 9, 2010, Index Holdings (株式会社インデックス・ホールディングス) announced its renaming to Index Corporation (株式会社インデックス), to be confirmed on the 15th shareholders meeting on 25 November 2010, effective on 1 December 2010. On June 27, 2013, following an investigation for fraud, Index Corporation filed for civil rehabilitation bankruptcy due to a debt consisting of 24.5 billion yen.
On September 18, 2013, it was reported that Sega Sammy Holdings had won a bid to acquire Index for 14 billion yen. Sega Sammy Holdings denied taking over Index Corporation at first, however it announced later that day that Index Corporation would sell the digital game business, contents and solution business, and amusement business to Sega Dream Corporation (株式会社セガドリーム), a subsidiary of Sega Corporation established on 2013-09-05, effective on 2013-11-01. The sales covered fixed assets and intellectual property assets of the announced operations, which included Atlus Holding, Inc. (parent company of Index Digital Media, Inc.), Tiger Mob Limited, Index Corp (Thailand) Ltd., Mobi Town Ltd. However, liabilities including interest-bearing debts would not be taken over. On November 1, 2013, Sega announced that it will rename its subsidiary, Sega Dream Corporation, to Index Corporation (株式会社 インデックス). On February 18, 2014, Sega and Index Corporation announced the separation of Index Corporation's contents and solution businesses into a new subsidiary under the name 'Index Corporation' (株式会社インデックス), while renaming the 'old' Index Corporation and its remaining digital game business division into 'Atlus' (株式会社アトラス), effective on April 1, 2014. The new Atlus would also include the foreign subsidiary Index Digital Media, Inc., which would be renamed to Atlus U.S.A., Inc. at the effective establishment day of the new Atlus.
On May 28, 2014, Masami Ochiai, Chairman of the former Index Corporation, and his wife Yoshimi Ochiai, president of the company, were arrested by the Tokyo District Public Prosectors Office on suspicion of falsifying stock reports for the company. 
- Index Corp (Thailand) Ltd.: Established in April 2002 as mobile content and service provider in Thailand.
- Interchannel: Japanese videogame developer formerly owned by NEC.
- Index Magazines Corporation (株式会社インデックス・マガジンズ): On 22 August 2005, Index Magazines was merged into Index Communications Corporation.
- Nikkatsu Corporation (日活株式会社): On 30 November 2005, Index Corporation announced sales of Nikkatsu Corporation to SKY Perfect Communications Inc., to be completed on December 2005.
- C&C Media Co.,Ltd (株式会社シーアンドシーメディア): An online video game publisher. On 1 February 2010, Index Holdings announced the sale of its C&C shares to Perfect World Co.,Ltd. On 26 March 2010, the sales of C&C to Perfect World Europe B.V. was formalized, to be completed on 31 March 2010.
- POLLEX kabushikigaisha (POLLEX株式会社): On 8 July 2009, Index Holdings announced selling all of its 204 (20.4%) shares of POLLEX to Hyundai-Index Corporation, to be closed on 15 July 2009.
- Hyundai-Index Corporation (現代インデックス株式会社): On 8 July 2009, Index Holdings announced selling all of its 306 (30.6%) shares of Hyundai-Index Corporation to Hyundai-Index Corporation, to be closed on 15 July 2009.
- Index Europe Holdings Limited: On 10 December 2009, Index Holdings announced disbanding Index Europe Holdings Limited, effective on 30 June 2010. The Index Multimedia SA owned by Index Europe Holdings Limited would operate under Index Holdings.
- Netindex ES (株式会社ネットインデックス・イー・エス): Communication device company owned by Netindex Inc. The company was established in 2005-09. On 12 August 2010, Index Holdings and Netindex Inc. announced merging Netindex ES into Netindex Inc., effective on 1 November 2010.
- net mobile? (株式会社ネットモバイル): Audio visual, data, image communication machine, software marketing company owned by Netindex Inc. On 12 August 2010, Index Holdings and Netindex Inc. announced merging net mobile into Netindex Inc., effective on 1 November 2010.
- Atlus Co., Ltd. (株式会社アトラス): A video game company. On 21 November 2006, Index Holdings announced the acquisition of Atlus Co., Ltd. beginning on 30 October 2006 and closed on 20 November 2006 via the purchase of 7.7 million (54.93%) stocks (77,000 votes/54.96% voting rights). Atlus Co., Ltd. became a consolidated Index Holdings subsidiary as of 29 November 2006. On 15 April 2010, Index Holdings announced ATLUS Co., Ltd. became a wholly owned subsidiary of Index Holdings via share exchange, effective on 10 May 2010. On 30 August 2010, Index Holdings announced its merger with ATLUS Co., Ltd. and Index Corporation, with Index Holdings becoming the surviving company, effective on 1 October 2010. After the merger, Index Corporation would continue to operate ATLUS's business under the ATLUS brand.
- Index Corporation (株式会社インデックス): A mobile division under Index Holdings. On 30 August 2011, Index Holdings announced its merger with ATLUS Co., Ltd. and Index Corporation, with Index Holdings becoming the surviving company, effective on 1 October 2011.
- Madhouse Inc. (株式会社マッドハウス): On 8 February 2011, Nippon Television became Madhouse's primary stockholder, via a third-party allocation of new shares.
- Rosso Index K.K. (株式会社ロッソインデックス): On 29 October 2009, Index Holdings announced the acquisition of GONZO Rosso K.K. from Chushoukigyou service kikou kabushikigaisha, and becoming a subsidiary of Index Holdings, effective on 30 October 2009. On 1 February 2010, GONZO Rosso K.K. (株式会社ゴンゾロッソ) was renamed to Rosso Index K.K. (株式会社ロッソインデックス). On 2011-07-27, Index Corporation announced selling its 89.33% stake (700,035 shares) of Rosso Index K.K. to C FACTORY Co.,Ltd. (株式会社シィファクトリィ) and retaining 6.96% stake (54,561 shares), with sales began on 2011-08-01. GOLDSKY ACCESS INTERNATIONAL,Inc. and Goldsky DigitalTechnology Ltd. subsidiaries owned by Rosso Index K.K. would also be no longer the sub-subsidiaries of Index Corporation.
- Netindex Inc. (株式会社ネットインデックス): Mobile and wireless service provider. The company was renamed from HONDA ELECTRON CO.,LTD. (本多エレクトロン株式会社) to Netindex Inc. on 22 August 2005. Netindex Inc. was renamed to NCXX Inc. (株式会社ネクス) in 2012-12.
- TEMO Inc. (株式会社テモ): A search application provider. On 28 September 2012, Index Corporation announced merging TEMO Inc. into Index Corporation, effective on 1 November 2012.
- Style Index (スタイル・インデックス株式会社): Renamed from YOSHINAGA CORPORATION (ヨシナガ株式会社) on 22 August 2005.
- Index Media (インデックス ミーメディア株式会社): Renamed from Indy Inc. (株式会社インディ) on 22 August 2005.
- Index Multimédia SA (インデックス・マルチメディア): On 3 August 2004, Index Group announced the acquisition of 66.65% shares of 123 Multimedia SA by Index Corporation, and becoming a subsidiary of Index Corporation. On 15 December 2005, Index Intercontinental Holdings Ltd acquired the 123 Multimedia shares held by Patrick Abadie and his wife via the G5 Holding Company, increasing Index Intercontinental Holdings Ltd's total capital holdings in 123 Multimedia to 70.15%. On 14 December 2005, 123 Multimedia's board of directors approved 123 Multimedia's company name change to Index Multimedia. Toulouse Court of Commerce decided assigning Index Multimédia SA's activity and Index Multimédia SA's subsidiary SASU TECHNIQUES MODERATION & CONVERGENCES to the benefit of the company's former executive Mr. Philippe Pisani acting for a simplified limited company (French SAS). Following the transfer, both entities were dissolved in 2013-10-17.
- Dynamo amusement, Inc. (株式会社ダイナモアミューズメント): A CG production studio, providing contents for movies, games and commercials, established on 2004-10-01 as Dynamo Pictures (株式会社ダイナモピクチャーズ). In 2011-07-19, Dynamo Pictures was renamed to Index Amusement, Inc. (株式会社インデックス・アミューズメント). In 2013-12-26, Index Amusement, Inc. was renamed to Dynamo amusement, Inc.
- Index Digital Media, Inc. (インデックス・デジタルメディア): Formerly Atlus U.S.A., Inc. It acts as a video game publisher and licensor for North American and European markets. The company was renamed to its former name, Atlus U.S.A., Inc., after the split of Index Corporation and became the subsidiary of the new Atlus.
- "Implementing Group Structure Reform" (PDF). Sega Sammy Holdings. 16 June 2015. Retrieved 2 October 2015.
- "Grenoble Foot 38 celebrates the long awaited opening of its new professional soccer stadium, `Stade des Alpes`". Index Corporation. Retrieved 26 January 2011.
- "Index Holdings to Change Company Name". Reuters. 9 November 2010. Retrieved 23 September 2012.
- Atlus Games' Index Corporation Files for Civil Rehabilitation Bankruptcy
- Shigeru Sato & Takahiko Hyuga (18 September 2013). "Sega Said to Win Auction to Buy Bankrupt Japan Gamemaker Index". Bloomberg. Retrieved 18 September 2013.
- Nikkei: Sega Sammy to Buy Out Atlus Games' Index Corporation
- "Notice of Conclusion regarding Business Transfer Agreement of Index Corporation" (PDF). Sega Sammy Holdings Inc. 18 September 2013. Retrieved 18 September 2013.
- 当社子会社の事業譲受に関するお知らせ (in Japanese). Sega Corporation. 1 November 2013. Retrieved 2 November 2013.
- 2014-06-17 Index Chairman's, Ochiai couple arrested for false earnings report,
- 日活株式 一部譲渡のお知らせ
- Acquisition of Nikkatsu Corporation Shares
- 当社子会社（Index Europe Holdings Limited）の解散及び清算に関するお知らせ
- "Regarding tender offer results and subsidiary companies" (PDF). Retrieved 30 August 2010.
- 当社連結子会社の吸収合併に関するお知らせ （簡易合併・略式合併）
- インデックス・ホールディングス、連結子会社の吸収合併に関するお知らせ ～グループ価値最大化を図りインデックス、アトラスの２社を吸収合併～
- 【補足】インデックス・ホールディングス、連結子会社の吸収合併に関するお知らせ アトラスブランドについて
- "NTV to Make Madhouse Anime Studio Its Subsidiary". Anime News Network. 2011-02-08. Retrieved 2013-04-12.
- 当社子会社（株式会社アトラス）における 株式会社ゴンゾロッソの株式取得（子会社化）に関するお知らせ
- 2010/02/01 社名変更のお知らせ
- 2011/08/1 親会社の異動に関するお知らせ
- "Index Holdings to Sell Shares of Subsidiary". Reuters. 27 July 2011. Archived from the original on 19 September 2013.
- インデックス、欧州最大級のモバイルコンテンツプロバイダー123 Multimedia社 を買収インデックスグループ来期780億円超の売上に。 圧倒的な展開力をもつグローバルメディアカンパニーとして躍進。
- INDEX INCREASES ITS CAPITAL HOLDINGS IN 123 MULTIMEDIA
- 123 becomes Index Multimedia
- INDEX MULTIMEDIA, decision from the Tribunal de Commerce of Toulouse
- INDEX MULTIMEDIA : Decision of the Toulouse Court of Commerce
- DYNAMO AMUSEMENT
- Official website (Japanese)