Yen Press publishes the manga in North America, and it describes the story:
Three years after the Sword Art Online incident, Kirito dives into a revamped Aincrad (now known as Ainground) in the new VRMMO Sword Art: Origin. As he progresses through the game with old friends and new, he meets a mysterious girl…
The Sword Art Online: Hollow Realization game shipped for PlayStation 4 and PlayStation Vita in Japan in October 2016, and in North America and Europe in November 2016. The game later received a PC release in October 2017. Bandai Namco Entertainment will release the Nintendo Switch version in Japan on April 25, and in the West on May 24.
CMX Manga licensed Hirokawa and Ichiro Sakaki's Polyphonica: Cardinal Crimson manga in 2009. The company published the first volume of the nine-volume series in June 2010 before DC Comics shut down the imprint in July 2010. Hirokawa also drew the Wake Up, Girls! Shichi-nin no Idol manga based on the Wake Up, Girls!: The Movie anime.
Source: Sword Art Online: Hollow Realization volume 5