SELECT 
  pfv.feature_id, 
  pfv.product_id, 
  pfv.variant_id, 
  gp.group_id 
FROM 
  cscart_product_features_values AS pfv 
  INNER JOIN cscart_product_variation_group_products AS gp ON pfv.product_id = gp.product_id 
  INNER JOIN cscart_product_variation_group_features AS gpf ON gpf.group_id = gp.group_id 
  AND gpf.feature_id = pfv.feature_id 
WHERE 
  pfv.lang_code = 'ja' 
  AND gp.group_id IN (43, 29, 52, 33, 53, 45)

Query time 0.00371

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "gpf",
      "access_type": "index",
      "possible_keys": ["PRIMARY", "idx_group_id"],
      "key": "PRIMARY",
      "key_length": "6",
      "used_key_parts": ["feature_id", "group_id"],
      "rows": 46,
      "filtered": 100,
      "using_index": true
    },
    "table": {
      "table_name": "pfv",
      "access_type": "ref",
      "possible_keys": [
        "PRIMARY",
        "fl",
        "lang_code",
        "product_id",
        "fpl",
        "idx_product_feature_variant_id"
      ],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["feature_id"],
      "ref": ["cscart_purchase_fl_com.gpf.feature_id"],
      "rows": 3,
      "filtered": 58.7939682,
      "attached_condition": "pfv.lang_code = 'ja'",
      "using_index": true
    },
    "table": {
      "table_name": "gp",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY", "idx_group_id"],
      "key": "PRIMARY",
      "key_length": "6",
      "used_key_parts": ["product_id", "group_id"],
      "ref": [
        "cscart_purchase_fl_com.pfv.product_id",
        "cscart_purchase_fl_com.gpf.group_id"
      ],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "gp.group_id in (43,29,52,33,53,45)",
      "using_index": true
    }
  }
}

Result

feature_id product_id variant_id group_id
7 135 18 29
7 200 18 29
7 201 19 29
7 202 19 29
7 203 20 29
7 204 20 29
7 134 18 33
7 219 18 33
7 220 19 33
7 221 19 33
7 222 20 33
7 223 20 33
7 128 18 43
7 256 19 43
7 257 20 43
7 137 18 45
7 260 19 45
7 261 20 45
7 262 18 45
7 263 19 45
7 264 20 45
7 132 18 52
7 283 19 52
7 284 20 52
7 127 18 53
7 285 19 53
7 286 20 53
8 135 26 29
8 200 27 29
8 201 26 29
8 202 27 29
8 203 26 29
8 204 27 29
8 134 26 33
8 219 27 33
8 220 26 33
8 221 27 33
8 222 26 33
8 223 27 33
9 137 29 45
9 260 29 45
9 261 29 45
9 262 31 45
9 263 31 45
9 264 31 45