UPDATE: It turns out the bonus character illustrations are retailer exclusives. The one for Kat is only available when ordering from Animate, while the one with Raven is only available when ordering from Gamers.
The Gravity Rush 2 manga, which is currently being serialized in the monthly “Comic Alive” magazine in Japan, is receiving its first standalone release. The first volume is being published by Kadokawa and will be released on January 23 in Japan. Featuring a total of 212 pages, the volume costs ¥ 648 (around $5.9 / €4.8). I’m assuming it will contain all the chapters released until now, which comprise the story of the game’s first chapter (Banga). Bonus character illustrations of Kat and Raven are also included.
The volume is currently up for preorder at various online retailers such as Amazon Japan. Keep in mind the manga is entirely in Japanese, although the story doesn’t deviate too far from that of the game.
You can also get it at bookwalker too, but its in jp as well.