Combine miso paste, sake, soy sauce, and sugar in a small bowl.
STEP 2
Heat oil in a skillet over medium heat. Add scallops; cook 3 to 4 minutes. Flip scallops; cook until no longer translucent and cooked through, about 1 minute more.
STEP 3
Reduce heat to low; let the skillet cool down for 1 minute. Add miso sauce; cook about 3 minutes, thinning with water if necessary. Add butter; stir until melted.