Mr. Sugarcube

Originally Gustavo's subordinate who currently works for the Daily Days. This long faced, lanky character is never seen without his box of sugarcubes either munching on them or offering them. It is not until the last episode that his name is revealed when he offers a sugar cube to the President of the Daily Days—and is referred to as Kakuzatou-kun or Mr. Sugarcube. Sugarcube may be one of the few people who have seen the face of the President of the Daily Days as he had to go behind the desk piled with books and papers to give him a sugar cube.

In the light novels his name is revealed to be, Rubik.

(Source: Wikipedia)