A memory system including a nonvolatile memory and a controller configured to control the nonvolatile memory, and a method executed by the memory system, wherein the controller fetches a first command in a submission queue on a memory of a host to a first queue in the memory system and executes the first command, checks contents of a subsequent command in the submission queue or another submission queue while leaving the subsequent command in the submission queue or the other submission queue, fetches the subsequent command to a second queue in the memory system, and executes the subsequent command and the first command in parallel, when the subsequent command is a command executable during the execution of the first command.