What Sega is doing with Chaos Heroes Online is pretty interesting. They licensed the rights to the PC game better known as Chaos Online in other regions and added Sega crossover characters. Selvaria Bles from Valkyria Chronicles and Ulala from Space Channel 5 are exclusive to the Japanese version.
Now, Chaos Heroes Online is getting guests from Guilty Gear. Dizzy from Guilty Gear XX Accent Core Plus is in the game.
At one time, Sega held the rights to Guilty Gear with Arc System Works. This happened when Sega and Sammy merged, but Sammy was the owner of Guilty Gear. The rights are back with Arc System Works and the Chaos Heroes Online cameos are the first collaboration with Sega since Arc System Works reacquired the rights.