Hi Sungmin,
for this task I would recommend the "SAP Business Connector". It can be downloaded from https://service.sap.com/sbc-download (no extra license fee required -- just a one-time registration of your S-User).
Among many other things, the SAP BC contains an automatic IDoc Adapter that allows receiving IDocs from SAP and mapping them to other data formats, and a Database Adapter that you could use in this case to insert the IDoc data into the Customer Master table(s) of the mSFA system.
See the "SAP Adapter Guide" for how to setup the SAP BC to receive IDocs from SAP and the "Built-In Services Guide" for how to use the database services. (Documentation is available on the same download page above.)
Best Regards, Ulrich