Structure of Exotic Nuclei Based on Nuclear Force

We present a novel method which enables us to perform shell-model calculations with several major shells (e.g., sd+pf). We present various observables, giving the first shell-model description for the island of inversion without two-body matrix elements fitted to experiment. Multiple particle–hole excitations over the N = 20 magic gap is shown to be crucial for the structure of ^30,31Mg, as an example.