You can retrieve network Cell ID and Location Area Code in order to determine the approximate location of your device by issuing AT commands to your device. Please note: AT commands may vary depending on your device, so you will need to refer to your device manufacturer's documentation for detailed instructions.
Using Air SIM for Japan
Cell ID and Location Area Code is provided by NTT DoCoMo's network functionality. You can get them by issuing "AT+CGREG?" AT command from your device:
AT+CGREG? +CGREG: 0, 1, "0021", "0404404F", 4
In above case, "0021" is the Location Area Code and decimal converted value of "0404404F" is the Cell ID.
You can combine this information with the SIM MCC (Mobile Country Code) and MNC (Mobile Network Code) in Google Maps Geolocation API to find the device's approximate location. For Air SIM for Japan, the MCC is 440 and the MNC is 10.
Using Air SIM for Global
Getting the Cell ID and Location Area Code will depend on the local roaming carrier's network functionality. Please refer to the carrier's instruction guides for further information.