Molecules (luciferase and luciferin) involved in bioluminescence are widely used as tools for gene expression monitoring, in vivo imaging analysis, and various assays. Until today, various luciferases and luciferins have been identified from various animals, such as firefly (Hotaru) and Cypridina (Umihotaru). However, there are still a lot of unknown or poorly studied luminous organisms all over the world. Especially, luminous marine animals have much greater diversity than the terrestrial species. Thus, we are trying to find and understand novel bioluminescence systems for a development of game-changing tools.