Various methods have been researched to extend the interaction spaces around mobile devices. The method of using conductive ink extends touch interaction space using a sheet with a pattern of conductive ink, which is attached to a capacitive touchscreen. However, the extended area of the interaction space with this method depends on the size of the sheet on which the conductive ink can be printed. We propose a method of connecting sheets using conductive aluminum foil tape. As a test system and an application of this method, we fabricated a mobile virtual piano system with a two-octave keyboard and evaluated the reaction accuracy.