The objective of this article is to investigate the effect of counter magnet configuration of an interactive touchdown developing system on the behavior of the brushes using the discrete element method. The shape of the magnetic brush, its shearing force acting on a development roll, or the electric potential distribution were analyzed. The magnetic brushes in the nip were crowded when the counter magnet was installed in the development roll. Their velocities also fluctuated; the brushes were pulled into the nip and returned to only a slight degree. The shearing force increases in the presence of the counter magnet because the stiffness of the magnetic brush became high, owing to the strong magnetic field. In the experimental work the toner mass adhered onto the development roll under the uninstalled condition was much larger than that with the counter magnet installed because of the reduced shearing force. The electric potential distributions around the nip also fluctuated in the presence of multiple magnetic brushes. The adhered toner mass was found to be affected by not only the shearing force but also this fluctuation of the electric field.