Many people use smartphones as tools for social media and personal communication. However, the use of smartphones may cause other people’s antipathy and flaming, which is often due to the contents of input texts. This paper presents a Japanese software keyboard that uses visualization to promote positive text input. By visualizing the impressions of words, it allows the user to easily input texts with positive impressions. Although its layout and operation are the same as those of normal software keyboards used by many Japanese people, its prediction conversion bar shows colored words to express plausible positive or negative impressions that the words convey. In addition, if the user presses and holds onto words, their synonyms will be displayed, which allows converting negative words to positive ones keeping meanings. This paper presents the results of the experiment conducted to evaluate its design. In addition, to prove its usefulness, this paper presents the results of the experiment on its comparison with a normal keyboard.