Iwashi (sardine) is a small bluefish, typically about 10–20 cm long. It is rich in fat, offering a bold flavor, with its peak season from summer to autumn. The kanji "鰯" originates from "weak" (弱), reflecting its quick spoilage. As sushi, freshness is crucial, showcasing its rich, fatty taste and smooth texture.

"Aburi" is a noun derived from the verb "Aburu" (炙る) in Japanese, which means to lightly sear or grill the surface of ingredients using direct flame. Unlike general grilling methods that evenly cook the entire ingredient, Aburi involves searing only the surface while leaving the inside uncooked. It is a cooking technique that allows for a contrast in texture and a smoky flavor between the outer and inner parts of the ingredients. Aburi sushi (炙り寿司), where the surface of fatty fish such as salmon or tuna is seared, is a representative example of Aburi cuisine. Even mild white-fleshed fish like sea bream can be enhanced in flavor and texture by searing the skin.