There is widely approved that the East/Japan Sea may serve as a miniature test ocean for global changes, since she has many oceanic features including her own conveyer belt system. In this regards, PICES approved a CREAMS/PICES program, named EAST-I (East Asian Sea Time-series-I), promoting international cooperation over East/Japan Sea, especially among Japan, Korea and Russia. Since 2006, Ministry of Land, Transport and Maritime Affairs of Korea has supported the Korea EAST-I program to identify, quantify and model the dynamic processes governing the climate variability and their linkage to changes in marine ecosystem. Through the Korea EAST-I program, integrated time-series monitoring (e.g. E-RAP, UBIM) was successfully performed on various spatiotemporal scales in the East/Japan Sea. Furthermore, Korea EAST-I program has promoted successfully international cooperation on joint cruises and international workshops. We believe that the just started secondphase Korean EAST-I program would continue to serve as an important forum for active international cooperation in this area for the next five years. Some important results obtained during the past 5 years of Korea EAST-I program are presented.