Gyokuro (玉露) is a type of green tea produced in Japan. It contains theanine (an amino acid), caffeine, tannin and vitamin C. Gyokuro is known for its rich umami due to the high content of theanine, and this umami is responsible for its full-bodied mellow sweetness. Gyokuro has abundant theanine because of the way tea leaves are grown. While the standard sencha is grown in the full sun, tea leaves for gyokuro are covered by sheets for 20 to 30 days before harvest. Containing a significant amount of tips and young shoots, gyokuro is relatively high on caffeine. In comparison to coffee, however, gyokuro’s caffeine is subtler as the theanine has a calming effect.