Realistic animation of soft objects such as cloth is essential for plausible character animation. Many techniques have been proposed for the simulation of soft objects, and most of them are based on numerical integration. Among the techniques, the implicit integration method is the most likely technique for real-time environments, since it allows large time steps for cloth simulation by ensuring the stability of systems. However, the most critical flaw of the implicit method is that it involves a large linear system.This paper presents a fast animation technique for animating soft objects based on mass-spring model with an approximated implicit method, which does not involve linear system solving. The proposed technique stably updates the state of $n$ mass-points in O(n) time when the number of total springs are O(n). Because the mass-spring model shows a super-elastic effect, the excessively deformed springs (i.e., super-elongated springs) should be adjusted for reality. This paper presents an efficient inverse dynamics process to adjust the super-elongated springs.