Nuklear : Unicode character test ( based on https://github.com/vurtun/nuklear/blob/master/demo/glfw_opengl3/main.c )

main.c

/* -*- encoding: utf-8; -*- */
/* nuklear - v1.17 - public domain */

/* Unicode character test based on:
 * https://github.com/vurtun/nuklear/blob/master/demo/glfw_opengl3/main.c */

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdarg.h>
#include <string.h>
#include <math.h>
#include <assert.h>
#include <math.h>
#include <limits.h>
#include <time.h>

#include <GL/glew.h>
#include <GLFW/glfw3.h>

#define NK_INCLUDE_FIXED_TYPES
#define NK_INCLUDE_STANDARD_IO
#define NK_INCLUDE_STANDARD_VARARGS
#define NK_INCLUDE_DEFAULT_ALLOCATOR
#define NK_INCLUDE_VERTEX_BUFFER_OUTPUT
#define NK_INCLUDE_FONT_BAKING
#define NK_INCLUDE_DEFAULT_FONT
#define NK_IMPLEMENTATION
#define NK_GLFW_GL3_IMPLEMENTATION
#include "../../nuklear.h"
#include "nuklear_glfw_gl3.h"

#define WINDOW_WIDTH 1200
#define WINDOW_HEIGHT 800

#define MAX_VERTEX_BUFFER 512 * 1024
#define MAX_ELEMENT_BUFFER 128 * 1024

#define UNUSED(a) (void)a
#define MIN(a,b) ((a) < (b) ? (a) : (b))
#define MAX(a,b) ((a) < (b) ? (b) : (a))
#define LEN(a) (sizeof(a)/sizeof(a)[0])

/* (Not complete) Glyph range table for Japanese.
 * [NOTE] Tables for some Chinese, Cyrillic and Korean are already embedded as 'nk_font_chinese_glyph_ranges', etc.
 */
const nk_rune nk_font_japanese_glyph_ranges[] = {
  0x0020, 0x00FF,
  0x2200, 0x22FF, // Mathematical Operators
  0x3000, 0x303F, // CJK Symbols and Punctuation
  0x3040, 0x309F, // Hiragana
  0x30A0, 0x30FF, // Katakana
  0x0370, 0x03FF, // Greek and Coptic
  0xFF00, 0xFFEF, // Halfwidth and Fullwidth Forms
  0x4E00, 0x9FFF, // CJK Unified Ideographs
  0
};

/* ===============================================================
 *
 *                          EXAMPLE
 *
 * ===============================================================*/
/* This are some code examples to provide a small overview of what can be
 * done with this library. To try out an example uncomment the include
 * and the corresponding function. */
/*#include "../style.c"*/
/*#include "../calculator.c"*/
/*#include "../overview.c"*/
/*#include "../node_editor.c"*/

/* ===============================================================
 *
 *                          DEMO
 *
 * ===============================================================*/
static void error_callback(int e, const char *d)
{printf("Error %d: %s\n", e, d);}

int main(void)
{
    /* Platform */
    static GLFWwindow *win;
    int width = 0, height = 0;
    struct nk_context *ctx;
    struct nk_color background;

    /* GLFW */
    glfwSetErrorCallback(error_callback);
    if (!glfwInit()) {
        fprintf(stdout, "[GFLW] failed to init!\n");
        exit(1);
    }
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
#ifdef __APPLE__
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif
    win = glfwCreateWindow(WINDOW_WIDTH, WINDOW_HEIGHT, "Demo", NULL, NULL);
    glfwMakeContextCurrent(win);
    glfwGetWindowSize(win, &width, &height);

    /* OpenGL */
    glViewport(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT);
    glewExperimental = 1;
    if (glewInit() != GLEW_OK) {
        fprintf(stderr, "Failed to setup GLEW\n");
        exit(1);
    }

    ctx = nk_glfw3_init(win, NK_GLFW3_INSTALL_CALLBACKS);
    /* Load Fonts: if none of these are loaded a default font will be used  */
    /* Load Cursor: if you uncomment cursor loading please hide the cursor */
    {struct nk_font_atlas *atlas;
    nk_glfw3_font_stash_begin(&atlas);

    /* >>> Use your favorite font here. */
    /* ex.) GenShinGothic : http://jikasei.me/font/genshin/ */
    struct nk_font_config conf = nk_font_config(0);
    conf.range = &nk_font_japanese_glyph_ranges[0];
    struct nk_font *genshin = nk_font_atlas_add_from_file(atlas, "../../extra_font/GenShinGothic-Normal.ttf", 22, &conf);
    nk_glfw3_font_stash_end();
    nk_style_set_font(ctx, &genshin->handle);}
    /* <<< Use your favorite font here. */

    /* style.c */
    /*set_style(ctx, THEME_WHITE);*/
    /*set_style(ctx, THEME_RED);*/
    /*set_style(ctx, THEME_BLUE);*/
    /*set_style(ctx, THEME_DARK);*/

    background = nk_rgb(28,48,62);
    while (!glfwWindowShouldClose(win))
    {
        /* Input */
        glfwPollEvents();
        nk_glfw3_new_frame();

        /* GUI */
        if (nk_begin(ctx, "日本語", nk_rect(50, 50, 230, 250),
            NK_WINDOW_BORDER|NK_WINDOW_MOVABLE|NK_WINDOW_SCALABLE|
            NK_WINDOW_MINIMIZABLE|NK_WINDOW_TITLE))
        {
            enum {EASY, HARD};
            static int op = EASY;
            static int property = 20;
            nk_layout_row_static(ctx, 30, 80, 1);
            if (nk_button_label(ctx, "ボタン"))
                fprintf(stdout, "押されました\n");

            nk_layout_row_dynamic(ctx, 30, 2);
            if (nk_option_label(ctx, "かんたん", op == EASY)) op = EASY;
            if (nk_option_label(ctx, "難しい", op == HARD)) op = HARD;

            nk_layout_row_dynamic(ctx, 25, 1);
            nk_property_int(ctx, "圧縮率:", 0, &property, 100, 10, 1);

            nk_layout_row_dynamic(ctx, 20, 1);
            nk_label(ctx, "背景色:", NK_TEXT_LEFT);
            nk_layout_row_dynamic(ctx, 25, 1);
            if (nk_combo_begin_color(ctx, background, nk_vec2(nk_widget_width(ctx),400))) {
                nk_layout_row_dynamic(ctx, 120, 1);
                background = nk_color_picker(ctx, background, NK_RGBA);
                nk_layout_row_dynamic(ctx, 25, 1);
                background.r = (nk_byte)nk_propertyi(ctx, "#赤:", 0, background.r, 255, 1,1);
                background.g = (nk_byte)nk_propertyi(ctx, "#緑:", 0, background.g, 255, 1,1);
                background.b = (nk_byte)nk_propertyi(ctx, "#青:", 0, background.b, 255, 1,1);
                background.a = (nk_byte)nk_propertyi(ctx, "#α:", 0, background.a, 255, 1,1);
                nk_combo_end(ctx);
            }
        }
        nk_end(ctx);

        /* -------------- EXAMPLES ---------------- */
        /*calculator(ctx);*/
        /*overview(ctx);*/
        /*node_editor(ctx);*/
        /* ----------------------------------------- */

        /* Draw */
        {float bg[4];
        nk_color_fv(bg, background);
        glfwGetWindowSize(win, &width, &height);
        glViewport(0, 0, width, height);
        glClear(GL_COLOR_BUFFER_BIT);
        glClearColor(bg[0], bg[1], bg[2], bg[3]);
        /* IMPORTANT: `nk_glfw_render` modifies some global OpenGL state
         * with blending, scissor, face culling, depth test and viewport and
         * defaults everything back into a default state.
         * Make sure to either a.) save and restore or b.) reset your own state after
         * rendering the UI. */
        nk_glfw3_render(NK_ANTI_ALIASING_ON, MAX_VERTEX_BUFFER, MAX_ELEMENT_BUFFER);
        glfwSwapBuffers(win);}
    }
    nk_glfw3_shutdown();
    glfwTerminate();
    return 0;
}

It does not work for me, I keep getting "?" chars as an output.
Should I set any flag on VisualStudio or include any additional library?
https://ibb.co/fBWjiH