Marine subsurface hydrocarbon reservoirs and the associated microbial life in continental margin sediments are among the least characterized Earth systems that can be accessed by scientific ocean drilling. Expedition 337 will drill and study the hydrocarbon system associated with a deeply buried coalbed off the Shimokita Peninsula in the northwestern Pacific by coring to 2200 meters below seafloor (mbsf) using the riser drilling system of the Chikyu. This project aims explore the microbial ecosystem associated with the deep coalbed in oceanic sediments, a habitat that has not been accessed by previous scientific ocean drilling. Hence, the study area is an ideal natural subsurface laboratory to study the deep carbon cycle and the deep biosphere.