Very common "purple on green"
Originally uploaded by nofrills.
Lamium amplexicaule.
This can be seen almost anywhere. The flowers are tiny, like five or six millimeter long.
More pictures on this page (in Japanese) and this page (in English) and this page (ditto).
The common name in English is henbit deadnettle and Giraffe Head
In Japan, this flower/weed is called Hotoke-no-za (in Japanese, ホトケノザ or 仏の座), which means "Buddha's Place" because the leaves look like what Buddha is sitting on.
