Short answers, pulled from the story.
Namco x Capcom is a tactical role-playing video game developed by Monolith Soft and published by Namco for the PlayStation 2. It was released in Japan on the 26th of May 2005 and was never officially released outside Japan.
The game was not released internationally because of its large amount of text and the limited worldwide recognition of many of the characters it featured. A fan translation group called TransGen completed an unofficial translation in 2008 after two years of work.
Namco x Capcom was developed by Monolith Soft, a Namco subsidiary, and directed and written by Soichiro Morizumi, a former Banpresto employee known for his work on the Super Robot Wars franchise. The producer was Kouji Ishitani, who had previously served as an assistant director on Xenosaga Episode I.
The opening and ending themes were composed by Yuzo Koshiro, marking the first time he wrote vocal themes. The soundtrack also features arrangements of series themes, with Yasunori Mitsuda credited as the only arranger, working on his Xenosaga Episode I tracks. Both vocal songs were performed by Flair, with lyrics written by director Soichiro Morizumi.
Namco x Capcom sold nearly 117,000 units within weeks of its release, reaching total sales of 131,600 by the end of the year. This placed it among the top 100 best-selling games in Japan for that year.
The Namco x Capcom team collaborated with Banpresto on Super Robot Taisen OG Saga: Endless Frontier for the Nintendo DS in 2008 and its sequel Endless Frontier Exceed in 2010. Monolith Soft and Banpresto then co-developed Project X Zone for the Nintendo 3DS in 2012, and Project X Zone 2 followed in 2015, developed solely by Monolith Soft with additional Nintendo franchise characters.