Japan is the largest consumer of tuna in the world. Although the history of tuna consumption in Japan dates back to the Jomon period (10,000 to 300 BC), where tuna bones have been found in archaeological sites, tuna was considered a difficult fish to handle compared to other fish because it spoils easily and loses flavor when dried or salted. The turning point for tuna becoming a national fish in Japan was during the Edo period when soy sauce fermentation (shoyu-jozo) became widespread. Marinating tuna in soy sauce improved its taste and preserved it better. Soy-marinated tuna, known as "zukezuke," gained popularity as an ingredient in sushi. Toro, which is considered a high-grade ingredient today, was actually a discarded part back then because it had a high fat content and couldn't be marinated in soy sauce while maintaining its quality. It was only after the development of freezing technology in the 1960s that the general public could easily consume toro as sashimi. In Japanese, tuna is called "maguro" (鮪 まぐろ). There are two explanations for the origin of the pronunciation "maguro." One suggests that it comes from the words "me" (目, meaning eye) and "kuro" (黒, meaning black), referring to the black eyes of the tuna. The other explanation suggests that it comes from the phrase "makkuro sakamata" (真っ黒逆叉), describing the dark appearance of a tuna swimming upside down when viewed from a boat.