This paper proposes a new implicit integration technique that reproduces a stable cloth without introducing excessive damping forces. Semi-implicit integration methods have been widely used in cloth simulations because of their high stability and speed. Artificial internal damping forces are generated during the linearization process of the semi-implicit integration. The simulations become extremely stable due to the artificial forces; however, the forces significantly degrade the realism of cloth simulations, since they are generated with respect to rotational rigid motions, as well as internal deformations. Hence, we propose a new method to decrease the damping artifacts. The artificial internal damping forces are computed solely for pure internal deformations, and are stably incorporated into the dynamical system. Experiments show that our simulator can reproduce various cloth materials without excessive damping artifacts even in real-time.