A sheet or overlay has plasticity and covers a keyboard including a plurality of keys, provided with a standard key indication based on a given language environment. The sheet has regions facing the keys on the keyboard, and an optional key indication based on a language environment different from the given language environment is provided in the regions so as to be visible by an operator when the sheet covers the keyboard. If the operator's use language is different from a language of the standard key indication on the keyboard, the keyboard is covered by the sheet supporting the operator's use language. In this way, an electronic apparatus coupled to the keyboard is set to support the language environment of the operator.