The strangeness S = −2 baryon-baryon interaction is investigated directly from the fundamental
theory of the strong interaction, QCD. The HAL QCD method enables us to extract baryon
interactions from the Nambu-Bethe-Salpeter wave functions without using any experimental information.
We discuss the properties of the S=−2 baryon-baryon potentials which are calculated
by using the (almost) physical point gauge configurations with large lattice volume of (8.1fm)4
generated on the K-computer.