A degenerated character input method used in the 1990s enabled users to enter a hiragana character by single-tap to the key where multiple Japanese hiragana were allocated. This method might remain ambiguities in hiragana strings since it actually inputs a numeral code, though this was a very convenient way because of its easy-to-learn and easy-to-use manipulation. Taking this advantage, we tried to develop a smartphone application to encourage the information retrieval illiterates, especially for elderly. By restricting the retrieval field, we tried to reduce the canditates derived from ambiguous input, for uses' easy selection. Key tiles were also designed larger than other existing digit designs on a touch screen. A Who's who database is formed from the Wikipedia open source by collecting personal names containing "yomigana" and their URLs. Converted numeral codes were added. An application "Shirabetai" was developed and installed on the Android smartphones. This application was demonstrated to the test subjects and opinion were collected. Operation times and error rates were also collected. About 70% of subjects recognized the usefulness of the proposed single-tap input method and the application. This method was also presented positive from performance evaluations for the elderly to assist input work in information retrieval.