This is black oolong tea. It's by Suntory Corporation and said to have various fat-burning and digestive aid properties. Notice how the bottle design is quite slim. This is to keep the volume down because it's quite potent and strong compared to most other teas on the market here in Japan. They are mainly aiming it at middle age men who are starting to get a bit thick around the middle and want to slim down. Also, it's handy for drinking after eating something oily.