Full Code

BackendLogin.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

// Adds BACKND SDK namespace
using BackEnd;

public class BackendLogin {
    private static BackendLogin _instance = null;

    public static BackendLogin Instance {
        get {
            if(_instance == null) {
                _instance = new BackendLogin();
            }

            return _instance;
        }
    }
    
    public void CustomSignUp(string id, string pw) {
        Debug.Log("Requesting sign-up.");
        
        var bro = Backend.BMember.CustomSignUp(id, pw);

        if(bro.IsSuccess()) {
            Debug.Log("Sign-up successful. : " + bro);
        } else {
            Debug.LogError("Sign-up failed. : " + bro);
        }
    }
    
    public void CustomLogin(string id, string pw) {
        Debug.Log("Requesting login.");
        
        var bro = Backend.BMember.CustomLogin(id, pw);

        if(bro.IsSuccess()) {
            Debug.Log("Login successful. : " + bro);
        } else {
            Debug.LogError("Login failed. : " + bro);
        }
    }

    public void UpdateNickname(string nickname) {
        Debug.Log("Requesting nickname change.");

        var bro = Backend.BMember.UpdateNickname(nickname);

        if(bro.IsSuccess()) {
            Debug.Log("Nickname change successful : " + bro);
        } else {
            Debug.LogError("Nickname change failed : " + bro);
        }
    }
}

BackendManager.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System.Threading.Tasks;

// Adds BACKND SDK namespace
using BackEnd;

public class BackendManager : MonoBehaviour {
    void Start() {
        var bro = Backend.Initialize(true); // Initialize BACKND

        // Response value for BACKND initialization
        if(bro.IsSuccess()) {
            Debug.Log("Initialization successful : " + bro); // If successful, 'statusCode 204 Success'
        } else {
            Debug.LogError("Initialization failed : " + bro); // If failed, a 4xx statusCode error occurs 
        }

        Test();
    }

    // A method that allows synchronous methods to be called from asynchronous methods(cannot be accessed by the Unity UI)
    async void Test() {
        await Task.Run(() => {
            // BackendLogin.Instance.CustomSignUp("user1","1234"); // [Addition] BACKND sign-up(handled as comment)

            BackendLogin.Instance.CustomLogin("user1","1234"); // [Addition] BACKND sign-up
            
            BackendLogin.Instance.UpdateNickname("Desired nickname"); // [Addition] Change nickname
            Debug.Log("Test complete.");
        });
    }
}

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