1boy arisaka birthday bolt_action boots coat gk_cofun golden_kamuy gun happy_birthday hat hat_over_one_eye highres kepi legs_apart looking_at_viewer male_focus military_hat official_style pointing_weapon rifle scar scar_on_cheek scar_on_face scar_on_nose short_hair solo sugimoto_saichi weapon  1boy barefoot birthday collared_shirt expressionless full_body gk_cofun golden_kamuy hand_in_own_hair highres looking_at_viewer male_focus no_headwear pants scar scar_on_cheek scar_on_face scar_on_nose shirt short_hair sitting solo sugimoto_saichi sweat very_sweaty