Mobile21

On September 2, 1999, Nintendo and Konami announced the establishment of Mobile21, a joint venture focused on developing software for Nintendo consoles with network connectivity. As part of this initiative, Nintendo planned to release an adapter the following year to connect the Game Boy Color and Game Boy Advance to cell phones, enabling online interactions. The company also had plans to develop software for the future GameCube console. Each company invested ¥150 million in the joint venture.

Operations began on October 7, 1999, with an initial capital of ¥200 million, evenly split between Nintendo and Konami. However, each company retained only 15% of the stock, leaving 70% available to grant to employees in anticipation of an early public offering, part of an aggressive talent recruitment strategy.

The Mobile Adapter GB and the Mobile System GB service were unveiled at the Nintendo Space World event in August 2000. At the time, Nintendo planned to release them in December, however, delays establishing the service pushed the launch back to January 27, 2001, for a MSRP of ¥5,800.

The Mobile Adapter GB was not a commercial success, selling 80,000 units in its first year on the market, leading the Mobile System GB service to be discontinued after less than two years on December 14, 2002. The end of the Mobile Adapter GB also led to the end of Mobile21.

Mobile21 produced twelve games during its time in existence, six of which used the Mobile Adapter GB.