In case of emergency, you need NOT pay ¥10 for there calls from a public telephone. Just press the red button before you place the call. If you need a doctor or first-aid, contact your hotel front desk or ask someone around you.
You will notice that there are police boxes very often located by main street crossings in Japan, to keep an eye on people on the street and assist them to find their way to their destination. Japan's crime rate is very low compared to that of many other countries.
Lost and Found
If you left your bag or package in a railway station or other public area, go to the stationmaster's office or the nearest police box and ask for English-language assistance. If you left something in a taxi then go to your hotel's reception desk. Taxi drivers often bring the belongings back to your hotel.