Ah, so this is why you can’t select Silence in Moon Diver. The black ninja from Stanford is downloadable content.
A DLC pack makes the ninja, who appears as a rival in Moon Diver, the fifth playable character. Moon Diver also has a downloadable score attack stage. In "Flow" the screen automatically scrolls while you chop through enemies. While Moon Diver is a multiplayer game, score attack mode is solo.
The first wave of Moon Diver downloadable content will be available this week in Japan.