His approach is based on an illusion hole that allows for multiple users and direct manipulation. The approach is to have different projections for different users, that are not visible for others but that creates the illusion of interaction with a single object. It uses a display mask that physically limits the view of each user. Have a look at their SIGGRAPH Paper for more details . More recent work on this can be found on the webpage of Yoshifumi Kitamura’s web page 
|Example of the IllusionHole from .|
Over 10 years ago they worked on tangible user interfaces based on blocks. Their system is based on a set of small electronic components with input and output, that can be connected and used to create larger structures and that provide input and output functionality. See  and  for details and applications of Cognitive Cubes and Active Cubes.
He showed examples of interaction with a map based on the concept of electric materials. Elastic scroll and elastic zoom allow to navigate with maps in an apparently intuitive ways. The mental model is straight forward, as the users can image the surface as an elastic material, see .
One really cool new display technology was presented at last year ITS is a furry multi-touch display . This is a must read paper!
|The furry display prototype - from .|
 Yoshifumi Kitamura, Takashige Konishi, Sumihiko Yamamoto, and Fumio Kishino. 2001. Interactive stereoscopic display for three or more users. In Proceedings of the 28th annual conference on Computer graphics and interactive techniques (SIGGRAPH '01). ACM, New York, NY, USA, 231-240. DOI=10.1145/383259.383285 http://doi.acm.org/10.1145/383259.383285
 Ehud Sharlin, Yuichi Itoh, Benjamin Watson, Yoshifumi Kitamura, Steve Sutphen, and Lili Liu. 2002. Cognitive cubes: a tangible user interface for cognitive assessment. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems (CHI '02). ACM, New York, NY, USA, 347-354. DOI=10.1145/503376.503438 http://doi.acm.org/10.1145/503376.503438
 Ryoichi Watanabe, Yuichi Itoh, Masatsugu Asai, Yoshifumi Kitamura, Fumio Kishino, and Hideo Kikuchi. 2004. The soul of ActiveCube: implementing a flexible, multimodal, three-dimensional spatial tangible interface. Comput. Entertain. 2, 4 (October 2004), 15-15. DOI=10.1145/1037851.1037874 http://doi.acm.org/10.1145/1037851.1037874
 Kazuki Takashima, Kazuyuki Fujita, Yuichi Itoh, and Yoshifumi Kitamura. 2012. Elastic scroll for multi-focus interactions. In Adjunct proceedings of the 25th annual ACM symposium on User interface software and technology (UIST Adjunct Proceedings '12). ACM, New York, NY, USA, 19-20. DOI=10.1145/2380296.2380307 http://doi.acm.org/10.1145/2380296.2380307
 Kosuke Nakajima, Yuichi Itoh, Takayuki Tsukitani, Kazuyuki Fujita, Kazuki Takashima, Yoshifumi Kitamura, and Fumio Kishino. 2011. FuSA touch display: a furry and scalable multi-touch display. In Proceedings of the ACM International Conference on Interactive Tabletops and Surfaces (ITS '11). ACM, New York, NY, USA, 35-44. DOI=10.1145/2076354.2076361 http://doi.acm.org/10.1145/2076354.2076361