1girl, Sayori, birthday theme, happy expression, blue eyes, short coral pink hair, school uniform, white blouse, blue skirt, thigh-high socks, red bow, holding birthday cake, party hat, balloons, confetti, classroom setting, festive atmosphere, friends in background, colorful decorations, streamers, soft lighting, medium shot, cheerful mood, vibrant colors, detailed textures, celebration moment, joyful ambiance, high resolution, digital painting style.