The Murder of Sonic The Hedgehog is now available on Steam for free. It's a whodunnit point-and-click adventure/visual novel in which you must investigate the murder of the blue blur who, among the others in the Sonic cast, was celebrating Amy Rose's birthday on a train.
The Murder of Sonic The Hedgehog features fully hand-drawn landscapes and characters, which may or may not be canon. It's not developed by the Sonic Team, however, but by the folks who run the legendary Sonic The Hedgehog socials.
This is a funny April Fools joke. Less about deceiving people about something or joking about a topic that people might desire to have. More about committing to a bit without causing harm to others.
This isn't the first time Sega has released a silly game on a silly day. Amplitude, a company established by Sega for its Endless series of games, has released a visual novel based on Horatio from Endless Space in 2019.
Hyenas, the upcoming shooter from Creative Assembly (also under Sega), revealed a character who murders people while cosplaying as Sonic.