The granddaddy of sushi: Narezushi, the most primitive form of sushi, is a world away from your California rolls and sliced sashimi. Dating back to the 10th century, this fermented fish was preserved with salt and raw rice, eventually giving way to the nigiri (sliced seafood atop rice) we know and love today. It's still common in Japan's Shiga prefecture.

Fresh imports: The earliest form of sushi is fermented fish, pickled with rice -- a practice that was common in much of Southeast Asia by the 2nd century CE. It's thought to have migrated to Japan around the 8th century, but written documentation of "narezushi" didn't appear until the 10th century.

A household staple: Around Lake Biwa -- the largest lake in Japan, just north of Kyoto -- narezushi was a household staple and an important source of protein.

DIY dinner: In a time before refrigerators, families relied on rice and salt to ferment and preserve the fish -- usually kept layered in barrels -- in the hope of saving it for as long as possible. Narezushi can be made with yellowtail, mackerel or ayu, but in the Lake Biwa area, the most common type is funazushi -- made from nigorobuna fish.

Family time: Most families have their own distinct recipe, but all share a similar methodology. First, the fish is scaled, gutted and preserved in salt for some months. Then, it's combined with rice and left to ferment.

Better with age: As long as there's a dark storage space at room temperature, the fish can be left for decades. For many centuries, people ate only the fish and threw the fermented "stinky rice" out. But around the 1500s, people began consuming half-fermented fish and rice together -- thus paving the way for modern sushi.

The slice is right: To serve, sushi chefs will slice the fish into thin layers and arrange them atop a bed of rice in a beautiful pattern. Sometimes, they prepare narezushi as porridge (called ochazuke-rice with hot tea), or even fry it up like tempura.

The stinkier the better: No matter how it's prepared, narezushi is one of those divisive foods that will either make or break your dinner, due to the sushi's sewage-like aroma and sour taste. For connoisseurs, the stinkier the better.

Funazushi fan club: "The people who love funazushi, they really love it. The first time I tasted it, I was actually in high school, around 16 or 17 years old," says Ohashi. "I thought it was really gross." While he couldn't quite stomach it at first, Ohashi says the taste has grown on him over time.

Left to ferment: To Ohashi's knowledge, the oldest funazushi has been fermented for a century. The older it is, the rarer it is. Aged narezushi can cost hundreds of dollars, though the most common types will have aged for about one year.

Narezushi hounds: If you're in Japan, narezushi is actually pretty easy to find. For a high-quality sampling, travelers will find traditional vendors along the shores of Lake Biwa. Kimura is one such institution, selling the delicacy for more than 50 years.

The top shop: "Because the fish itself is scarce nowadays, people can't catch enough and we consider this a special meal... it's no longer a common thing," Akiko Higashimomo, a shopkeeper, tells CNN Travel. "It's reserved for family gatherings and special occasions. Because it has a distinctive strong taste it's not a thing that you eat every day."