Semiconductor storage device and memory system

To provide a semiconductor storage device and a memory system, capable of achieving a faster operation. A semiconductor storage device of an embodiment includes a first and a second memory cell, a first word line connected to the first memory cell and a second word line connected to the second memory cell, and a control circuit which responds to each of first and second command sets and executes a read operation. The control circuit can execute a first sequence which reads data using mutually different first to third voltages, and a second sequence which reads data using a voltage based on results of the first sequence. In a first memory cell read operation based on the first command set, the first sequence and the second sequence are continuously executed. In a second memory cell read operation based on the second command set, a second sequence based on results of the first sequence in the first memory cell read operation is executed.