「Chibi Dialog Free」is a uGUI that displays dialogs easily on the screen.
I think that it is useful mainly for iPhone and Android.
Click here for the paid version, which also allows you to place text input fields...
If the link is broken, please assume that it was not reviewed. :)

☆ Features ☆
・The background color can be set for each button.
・You can receive a callback when a button is pressed.
・A separate callback is also provided after the dialog is closed.
・The function to close the dialog by tapping on the outside of the dialog is also implemented. This feature can be enabled or disabled.

☆ How to use ☆
1. Add Prefab folder>ChibiDialog to the scene.
2. Add the following code to the variable declaration section of C# and attach it to the GameObject.
//------------------------------
public Chibi.Free.Dialog dialog;
//------------------------------
3. Drag the ChibiDialog added in step 1 to the "dialog" of the script in step 2.
4. Using the demo scene as a reference, write the code to display the dialog.

☆ Notes ☆
Additional text input fields are available only in the paid version.
This dialog cannot be displayed in multiple layers.
(Because I don't think it is beautiful in terms of UI.)

☆ Update notice ☆
If this dialog is well received, I'll implement an action sheet as well.