SELECT 
  lang.name, 
  lang.value 
FROM 
  cscart_language_values lang 
WHERE 
  lang.lang_code = 'ja' 
  AND lang.name IN (
    'jp_welcome', 'jp_dear_casual', 'jp_login_or_register', 
    'dear', 'profile_details', 'downloads', 
    'orders', 'view_comparison_list', 
    'jp_remise_payquick_registered_card', 
    'track_my_order', 'track_my_order', 
    'order_id', 'email', 'go', 'go_to_admin_panel', 
    'sign_out', 'register', 'jp_welcome', 
    'jp_dear_casual', 'jp_login_or_register', 
    'dear', 'profile_details', 'downloads', 
    'orders', 'view_comparison_list', 
    'jp_remise_payquick_registered_card', 
    'track_my_order', 'track_my_order', 
    'order_id', 'email', 'go', 'go_to_admin_panel', 
    'sign_out', 'register'
  )

Query time 0.00073

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "lang",
      "access_type": "range",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "392",
      "used_key_parts": ["lang_code", "name"],
      "rows": 16,
      "filtered": 100,
      "index_condition": "lang.lang_code = 'ja' and lang.`name` in ('jp_welcome','jp_dear_casual','jp_login_or_register','dear','profile_details','downloads','orders','view_comparison_list','jp_remise_payquick_registered_card','track_my_order','track_my_order','order_id','email','go','go_to_admin_panel','sign_out','register','jp_welcome','jp_dear_casual','jp_login_or_register','dear','profile_details','downloads','orders','view_comparison_list','jp_remise_payquick_registered_card','track_my_order','track_my_order','order_id','email','go','go_to_admin_panel','sign_out','register')"
    }
  }
}