The manga follows the beginning of the Sonic Colors game: Eggman has built a giant amusement park for everyone to enjoy. Sonic and Tails go to the amusement park to figure out what Eggman is up to.

A certain winter day. Hajime Mutsuki, the leader of the idol unit "Six Gravity," (a.k.a. Gravi) associated with Tsukino Talent Productions, aimlessly dropped by a secondhand bookstore and encountered Shun Shimotsuki, the leader of their sibling unit "Procellarum" (a.k.a. Procella). The two of them picked up the antique classic which was thought to be the original work of the stageplay they would be starring in: "Rabbits Kingdom." Though it should have been his first time hearing the title, a strange bothersome sensation befell him, almost as if it were stuck in the back of his head. To the perplexed Hajime, Shun gently smiled. "...Ah, this one. It's quite a nostalgic and beloved... story of us from another world." This is a "what if" story of a kingdom in some other world. (Source: Hakusensha, translated)

The spinoff manga centers on Satoshi Mukai, who once competed with Kai Ichinose in the Chopin Competition. Satoshi was so moved by Kai's performance, that he decides to pursue a career in the world of musical tuning. Satoshi needs to survive in an ordinary society while possessing a rare talent. (Source: Anime News Network)

From [MangaHelpers](https://www.mangaupdates.com/groups.html?id=1011): In the far future, there exists a vast region of space that is yet to be explored called the New Space. The levels of new discoveries and dangers are unknown. The Dian sisters, Reina and Rio, made a promise to each other that they will one day journey into New Space together. The two sisters were separated and Reina became a pilot of the commercial luxury cruise liner spaceship Folshion. Rio is a tomboy who seems to have no self consciousness that she is a girl and who finally finds her sister. Rio is allowed to stay on the Folshion granted she finds herself a role on the ship. Sisters united once again, begin dreaming about the adventure into the new territory [vyc]

Based on the PS3/360 game, Sonic Generations.

A hotel plans to work together with a nearby shopping center to attract more customers and improve their level of service. To help, they've brought in an excellent advisor, Kuon Kyouya, who uses his skills to figure out what customers want. Hopefully, the concierge service at the hotel will soon be at the platinum level! (Source: MangaHelpers)

New Sonic the Hedehog manga, based on the upcoming game, Sonic World Adventure (aka Sonic Unleashed).

Invited to another world, fighter pilot Tatsuno throws himself into a sky battle to hunt dragons with aces of various nationalities who were also summoned. But they have a secret... Different World Military Sky Action Begins! (Source: Kadokawa, translated)