RandomGuyHere9001 said it good, but let me add the details in case you’re lost:

I did this on the phone btw:

So when you go to the main page of Rent a Girlfriend there’s going to be three dots on the top right corner of the screen like this:

...

All you have to do is press it and it’ll open up a menu at the bottom of the screen. All you have to do is tap on what says this:

Change user flair

Then it’ll bring you to this page where it’ll show you all the different characters names like this:

Chizuru

Kazuya

Sumi

Ruka

Mami

Etc.

DO NOT PRESS THE NAME OF THE CHARACTER AND HIT APPLY(yet). What you actually do is that you press on the EDIT BUTTON at the top right corner.

Then it’ll show arrows on the right, so tap on the arrow that goes with the name you want to change/edit. Then it’ll bring you to another page that will bring up a key board.

Here’s the editing:

You can type the name of your character like normal, but if you take a look at the right it’ll show a smiley face and if you tap on it it’ll show the character faces that are emojis.

Now when you tap on the emoji, the keyboard will show it to you like this-> :Kazuya: <-emoji

So when I type my flair it looks like this:

:Kazuya:Kazuya x Chizuru:Chizuru:

It looks weird on the keyboard, but it will show up fine in the middle of the screen.

Then once your done it’ll bring you back to the character names then you just tap on the name you changed/edited and hit APPLY and congratulations you made your own new flair for everyone to see it!!!