I wrote about these a long time ago, but I just got my hands on the Black Bean. Mameshiba's insanely popular, they've spawned anime shows, a manga. They've even decided each type of bean has its own personality.
Black Bean here is described as "Has a tendency to to stare and likes to hide." So he's like the creepy stalker of the Mameshiba world, if the pure innocence of that world could have a stalker. What's the adorably cute version of a stalker? Black Bean would be that. Also, pink hippo sweat.