DeruChara is a novel mixed reality (MR) interface which can form mid-air images in free space. Our proposed system consists of depth sensor, projector, and mid-air imaging display. Mid-air imaging display can form mid-air images in free space with a size of 35 cm (W) x 30 cm (D) x 25 cm (H) with combining novel real imaging optics and linear actuator. A depth sensor detects the position and shape of blocks and users' hands and constructs terrain data. Based on the terrain data, mid-air images and physical objects can be mixed with a high level of geometrical consistency. Moreover, shadow projection provides a high sense of reality by improving the optical consistency. Users can experience a new interaction between mid-air images and physical objects. With DeruChara system, virtual characters which were once confined to the screen appear in front of your eyes and run around the real blocks. When the blocks are moved, characters also move in mid-air. DeruChara realizes a seamless combination between virtual and real world by extending the displaying area to the real world.