SELECT 
  lang.name, 
  IF(
    cscart_ult_language_values.value IS NULL, 
    lang.value, cscart_ult_language_values.value
  ) as value 
FROM 
  cscart_language_values lang 
  LEFT JOIN cscart_ult_language_values ON cscart_ult_language_values.name = lang.name 
  AND company_id = 1 
  AND cscart_ult_language_values.lang_code = lang.lang_code 
WHERE 
  lang.lang_code = 'en' 
  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', 'go', 'go_to_admin_panel', 
    'sign_out', 'sign_in', 'register', 
    'sign_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', 'go', 'go_to_admin_panel', 
    'sign_out', 'sign_in', 'register', 
    'sign_in'
  )

Query time 0.00077

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_ult_language_values",
      "access_type": "system",
      "possible_keys": ["PRIMARY"],
      "rows": 0,
      "filtered": 0,
      "const_row_not_found": true
    },
    "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 = 'en' 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','go','go_to_admin_panel','sign_out','sign_in','register','sign_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','go','go_to_admin_panel','sign_out','sign_in','register','sign_in')"
    }
  }
}