Dokudami / Houttuynia cordata / Chameleon Plant
This is a common plant, both in the wild, where it prefers the shade, and as a weed in the garden. It is native to a wide sweep of Asia, and the commonest way of referring to it in English appears to be the Latin name, at least in horticultural circles.
Although (as in the photo) the plant can be all-green, the ダミ (彩み) part of its name refers to the variations of coloration which occur (perhaps when exposed to more light). In the garden, the leaves are fringed with purple, often of a very dark shade. This accounts for one English name, "chameleon plant". (There are also variegated cultivars, in three colours - green, yellow and purple.)
The alternative name of 十薬 reflects its status as a folk medicine, reputedly good for a large number of ailments. The leaves of varieties in SE Asia are apparently eaten raw - on the other hand, the plant has a strong enough smell to make crouching down to photograph a mass of it somewhat unpleasant.