CUBE2 is a successor to CUBE (ascl:1805.018), a cosmological N-body simulation code emphasizing memory efficiency, computational performance, scalability, and precision. It employs a 3-level particle-mesh (PM) and particle-particle (PP) method to compute gravitational forces, where the resolution of the innermost PM layer and the PP force range are adaptive according to the clustering of the matter distribution to minimize computation time. Force accuracy is enhanced using optimized Green's functions. The code achieves high weak and strong scalability.