@felmue , @teastain
I have a good report.
I was able to change my address using this procedure based on everyone's advice.

1. remove the already installed M5Unit-EXTIO2 from the library folder.
2. download the latest library from here as a zip file and install M5Unit-EXTIO2-main.
3. wrote this sketch.

#include <M5Stack.h>
#include "M5_EXTIO2.h"

M5_EXTIO2 extio;

void setup() {
int t_erro = 0;
M5.begin();
t_erro = extio.begin(&Wire, 21, 22, 0x45);
if(t_erro){
M5.Lcd.print("Connect");
}else{
M5.Lcd.print("Error");
}
extio.setDeviceAddr(0x47);

}
void loop() {
}

Thanks to you guys for helping me solve the problem. Thank you so much!

@felmue
Oops, I found a mistake and will correct it.
t_erro = extio.begin(&Wire, 21, 22, 0x45);

However, even with this modification, "begin" still returns an error.

Thanks for your reply.

Hello, I have a question.
I want to implement two EXT.IO2 in M5stack basic.
To do this, I need to change the I2C address of one of them.
However, the program I made based on the EXT.IO2 sample sketch could not connect to the unit. (ERROR is responded on begin.) Please tell me what is the problem.
I don't think it's a hardware issue since UIFlow could change it... :(

#include <M5Stack.h>
#include "M5_EXTIO2.h"

M5_EXTIO2 extio;

void setup() {
int t_erro = 0;
M5.begin();
extio.begin(&Wire, 21, 22, 0x45);
if(t_erro){
M5.Lcd.print("Connect");
}else{
M5.Lcd.print("Error");
}
extio.setDeviceAddr(0x46);

}
void loop() {

}