1girl, adjusting_hair, arknights, armpits, arms_up, ass, back, beach_umbrella, bikini, black_bikini, breasts, closed_mouth, demon_girl, demon_horns, horn/wood, horns, large_breasts, long_hair, looking_at_viewer, looking_back, official_alternate_costume, outdoors, purple_eyes, red_hair, sitting, solo, surtr_(arknights), surtr_(colorful_wonderland)_(arknights), swimsuit, swimsuit_cover-up, umbrella