1. An apparatus for estimating a target character train from a predefined reference character train, said apparatus comprising a processor configured to: acquire a reference phoneme train related to the predefined reference character train, the reference phoneme train being indirectly representative of the reference character train by use of a limited plurality of kinds of particular phonemes; acquire a target phoneme train indirectly representative of the target character train by use of the particular phonemes; and identify, based on a comparison between the target phoneme train and the reference phoneme train, a character sequence in the reference character train that corresponds to a sequence of the particular phonemes in the reference phoneme train matching the target phoneme train.