From Sonic Retro
The following are instruction manuals for Sonic Mania.
English story for Mania Mode from Steam manual
Discovering a sudden dimensional breach in the atmosphere, evil genius Dr. Eggman detected a unique wave signature emanating from Angel Island. Realising that it could be a source of unspeakable power, he immediately dispatched his elite robot minions—the Hard Boiled Heavies (HBH)—to retrieve it.
Meanwhile, Sonic and Tails were also tracking the signal but arrived a little late to the party—the HBH were already there, excavating a mysterious gemstone out of the ground. As they did so, space time suddenly warped around them, catapulting them all to the Green Hill Zone.
As the HBH rush to deliver the gemstone to Dr. Eggman, it’s up to Sonic, Tails & Knuckles to stop them.
Don’t let the Phantom Ruby get into the wrong hands!
English story for Encore Mode from digital manual
However, as he attempts to retrieve the Phantom Ruby, he sees two figures captured in a trap box. They are none other than Mighty the Armadillo and Ray the Flying Squirrel, two friends who had joined Sonic on a previous adventure.
With no time to spare, Sonic takes off once again in search of the Phantom Ruby. And this time he's not alone—he has dependable friends to help him along the way!
- Sonic Mania digital manual for consoles: