According to Wikipedia (yeah, I know, but I'm pressed for time), a shrine literally holds a Japanese deity or Buddha. The Buddha in this temple is Yakushi Nyorai, the Buddha of Medicine and Mercy.
The shrines in Ueno are all part of a system of shrines called the Toeizan Kan'ei-ji, built by a priest named Tenkai and supported by the Shogun at the time, Tokugawa Ieyasu. The Japanese believed that evil things come from the northeast, so they built these temples around the northeast of the Imperial Palace to help protect it.
The Kanei'ji Temple, as it was called in the tour guide, is also the Kompon Chu-do, which, according to the flyer I got there, means "Central Hall". The original Central Hall was burned down in the Battle of Ueno in 1868 (I know nothing more about that battle), and the current one is much smaller than the original.
Like the rest of Ueno, there were no English signs around this, so I don't know what most of these buildings were. I know the first one is where the deity is housed, but I'm not sure about the rest.
|Okay, I remember this... This is a statue of a monk who was exceptionally holy. But I don't remember the rest.|
What interested me about this was that behind the Kanei'ji Temple is the Tokugawa Shogun Mausoleum. I couldn't go inside, but here is the outside: