We propose a technique to support writing activity in a confidential manner with a pen-based device. Autocorrect and predictive conversion do not work when writing by hand, and looking up unknown spelling is sometimes embarrassing. Therefore, we propose AmbientLetter which seamlessly and discretely presents the forgotten spelling to the user in scenarios where handwriting is necessary. In this work, we describe the system structure and the technique used to conceal the user"s getting the information.