3. The non-transitory computer-readable recording medium according to claim 1 , wherein: the specifying specifies a third group of data items that each include a tail character of the one or the plurality of search keyword, based on a tail character appearance map stored in the storage, the tail character appearance map indicating whether each character in the tail character appearance map is included as a tail character respectively in the plurality of data items, and the searching searches the one or plurality of search keywords utilizing the third group of data items.
3. The non-transitory computer-readable recording medium according to claim 1 , wherein: the specifying specifies a third group of data items that each include a tail character of the one or the plurality of search keyword, based on a tail character appearance map stored in the storage, the tail character appearance map indicating whether each character in the tail character appearance map is included as a tail character respectively in the plurality of data items, and the searching searches the one or plurality of search keywords utilizing the third group of data items. 4. The non-transitory computer-readable recording medium according to claim 3 , wherein: the specifying specifies the first data items from the third group of data items based on the character appearance map, and the searching searches the one or plurality of search keywords utilizing the first group of data items.