This is a sad day for Dragon Quest fans. Koichi Sugiyama passed away at the age of 90. The cause of death was due to a septic shock.
He may have a controversy of some very awful opinions and beliefs in the past that a lot of people (mostly Twitter nutjobs) find offensive and demands Square Enix to cancel him. Even I strongly disagree with his beliefs. But nonetheless he is a legendary music composer that changed the gaming industry and made what's so beloved about the Dragon Quest franchise. According to the Dragon Quest website, Sugiyama's final work was to compose music for Dragon Quest XII.
Dragon Quest won't be the same without him. May he rest in peace.