It's the old quantity-versus-quality problem. Though there are only a couple of private contemporary-art museums in Tokyo (the Watari-Um and the Hara), their shows are almost always good and focus on providing authoritative coverage of some of the domestic and international art scenes' most important figures.
Last week the Watari-Um Museum of Contemporary Art opened its summer exhibition, Carsten Nicolai's "Parallel Lines Cross at Infinity," featuring the youngest artist ever to hold a solo show at this most elite of Tokyo art institutions.
I was initially curious why the Watari would turn its space over to the relatively unknown Nicolai for four months. But seeing the show made it clear that the German installation artist, whose 36 years just barely squeak him into the "mid-career" category, is perfect for the place.