Hi Yutaka and team,
I am observing the behavior that looks like a bug. Here is how to reproduce it:
I start Tera Term 4.90 and New Connection window pops up. I want to establish serial port connection, but I know the default baud rate in my TERATERM.INI file is 19200, while I need to establish connection at 9600 speed. So, I click Cancel button in New Connection window go to menu Setup->Serial port, change baud rate to 9600 and click OK. As soon as I click OK in Serial Port setup window, Tera Term opens serial port connection. When I then go back to New Connection window my COM port is not available anymore.
I hope this is not as per design, because user does not expect to open connection by changing port settings.