The on-screen keyboard is widely used for text input in mobile devices such as smart phones and tablets. However, the screen area of such devices is not sufficiently wide for smooth input and poses a difficulty to users. Therefore, this paper proposes a gesture-based text entry method that is based on the property of Japanese Hiragana-50-phonemic-table with two-step finger gesture sequence. The first step gesture is to specify the row, such as “a ka sa ta na”, and the second is to specify the column, “a i u e o”. This method does not require a predetermined input area and can be used anywhere on the screen surface. We conducted experiments with ten test subjects who were accustomed to conventional flick entry and found that the proposed method was easy to learn. The input speed was estimated to about half the speed of the flick entry method. This can be attributed to the need for one stroke in flick entry based on-screen keyboards, while the proposed method requires two strokes. Further, the entry rate accuracy was observed to be 91.5%. The experimental results show that the proposed method is practically applicable as a new text entry method.