Ajuga decumbens キランソウ属 This is the kiran-sou(sou means grass) spotted during a satoyama country walk. They are native to Honshu and Kyushu island in Japan and can also be found on the mainland continent China. I saw some low-lying versions in our yard as well. Apparently they range from 5 – 15 cm high. See another version here.
Reference: Days of Plants by Ciaobou Hany.
NATURE IN JAPAN 