We present the SILVERRUSH program strategy and clustering properties investigated with ∼2000 Lyα emitters (LAEs) at z = 5.7 and 6.6 found in the early data of the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey exploiting the carefully designed narrow-band filters. We derive angular correlation functions with the unprecedentedly large samples of LAEs at z = 6-7 over the large total area of 14-21 deg2 corresponding to 0.3-0.5 comoving Gpc2. We obtain the average large-scale bias values of bavg = 4.1±0.2 (4.5±0.6) at z = 5.7 (z = 6.6) for L∗ LAEs, indicating a weak evolution of LAE clustering from z = 5.7 to 6.6. We compare the LAE clustering results with two independent theoretical models that suggest an increase of an LAE clustering signal by the patchy ionized bubbles at the epoch of reionization (EoR), and estimate the neutral hydrogen fraction to be xHI = 0.15-0.15+0.15 at z = 6.6. Based on the halo occupation distributionmodels, we find that the L∗ LAEs are hosted by dark-matter halos with an average mass of log(Mh/M) = 11.1-0.4+0.2 (10.8-0.5+0.3) at z = 5.7 (6.6) with a Lyα duty cycle of 1% or less, where the results of z = 6.6 LAEs may be slightly biased, due to the increase of the clustering signal at the EoR. Our clustering analysis reveals the low-mass nature of L∗ LAEs at z = 6-7, and that these LAEs probably evolve into massive super-L∗ galaxies in the present-day universe.