1. An assistance system comprising: an assistance device configured to assist movement of a care receiver; a microphone provided on the assistance device; a speech analyzer configured to analyze speech of at least one of a caregiver or the care receiver included in sound data acquired by the microphone and acquire information related to an action by performing search processing of a detection word included in detection word information in order from a start of sound data, when the detection word is detected, performing search processing on a restricted word included in restriction word information during a conversation portion that included the detection word, when no restriction word is detected in the conversation portion, searching all detection words included in the conversation portion, identifying information including at least one of the caregiver or the care receiver, and an assistance operation for the care receiver, and linking the identified information to the information related to the action, and when the restriction word is detected in the conversation portion, omitting processing of the identified information; an echo analyzer configured to analyze an echo included in the sound data and acquire information related to a location by performing search processing of a specified echo included in echo information in order from the start of sound data, and when the specified echo is detected by the search processing, identifying a room in which the speech was recorded by the microphone based on a specified reflection sound frequency and echo information as the information related to the location; a log data analyzer configured to acquire the information related to the action by identifying the assistance operation of the care receiver based on log data in which an operation history of the assistance device is recorded including a standing operation and a sitting operation of the care receiver by performing search processing of the log data of a transfer operation in which the standing operation and the sitting operation are performed in order, or of a movement between different rooms, and when the transfer operation or the movement between different rooms is detected by the search processing, identifying information including the location and the assistance operation from when the microphone recorded the speech based on the search processing, and linking the identified information of the caregiver or the care receiver to the information related to the action and the information related to the location: an action history information generator configured to generate action history information of at least one of the caregiver or the care receiver based on the information related to the action and the information related to the location generated by the speech analyzer, the echo analyzer, and the log data analyzer: and a report generator configured to generate an assistance report including contents of assistance operations received by the care receiver based on the action history information generated by the action history information generator, wherein the assistance system is configured to perform discarding processing on the sound data used by the speech analyzer, the echo analyzer, and the log data analyzer after the assistance report is generated, the action history information includes a context in which the caregiver uses the assistance device to assist the movement of the care receiver, and the context in which the caregiver used the assistance device to assist the movement of the care receiver is different from operations performed by the assistance device to assist the movement of the care receiver.