"Put a new lock on the fire door"
It seems to be a detached house, but it was like a two-family house. The guided door is indeed an iron fire door. It seems that this door separates the son and couple's area. She wanted to put a new lock on the door here.
It seems that there was some kind of family trouble, but I couldn't understand it well. It seems that he has many duplicate keys and does not want to increase the number of keys, but the lady who requested it seemed to think that a digital key could be attached for several tens of thousands of yen.
We cannot meet your request with the price of processing work on iron doors and digital locks (EPIC, etc.).
If she want to prevent her son and his wife from entering without permission, I suggested that you replace the cylinder and use a new key. If you throw away the old key and get a new one, even the son and wife who had the duplicate key so far will not be able to enter.
It was a little difficult to correct because the lock case was attached diagonally, but I was able to replace it with U9.MHD.