Double Olympic medallist PV Sindhu sailed into the pre-quarterfinals, but Lakshya Sen made an opening-round exit from the Kumamoto Masters Japan Super 500 tournament here on Wednesday. World number 20 Sindhu brushed aside Thailand’s Busanan Ongbamrungphan, ranked 11, by a scoreline of 21-12, 21-18 in 38 minutes in a one-sided first-round match. Earlier, Sindhu began sluggishly, quickly falling behind 1-5, …