Confronting a giant fish with just a harpoon, a battle of bare life
"I guess I just can't beat that fish..." murmured Kunpei Kosaka, who was on an expedition to an island near the southernmost tip of Japan, as he recalled his struggle with a giant fish there. Kosaka is a spearfisher who uses only a harpoon to spear giant fish while free-diving. In 2021, he caught a 189cm, 86.1kg dogtooth tuna, setting a new world record. He holds six world records, including other fish species, and this summer he is attempting to catch a dogtooth tuna weighing over 100kg.
"Dogtooth tuna are also known as 'devil fish,' and have sharp teeth in their mouths that are strong enough to swallow a human in one bite. If you harpoon them, they dive to the bottom of the ocean with great force, and if you get pulled into the rapids, it's all over. They're an opponent that you can't defeat unless you risk your own life, which is why I want to face them head on."
In fact, Mr. Kosaka was completely unable to swim until he entered university.
"Because I can't swim, I was curious about what was under the sea. I enrolled at Tokyo University of Marine Science and Technology to become an oceanographer, and by chance I joined a free-diving club, where I discovered the wonders of the ocean and spearfishing."
The moment I speared my first large flounder, I was overwhelmed by the vibrations transmitted from the harpoon.
"At that moment, I felt like I understood the true essence of spearfishing. It wasn't about wanting to catch a lot or eat a lot. I simply wanted to seriously challenge myself to catch a big fish that I was satisfied with, without any effort on my part."
Since then, he has spent more than 200 days a year at sea spearfishing.
"I was aiming for a giant Spanish mackerel in Japan, and just when I thought I'd got the harpoon in, about 20 sharks, each over 2m long, gathered around me. I swam to the boat, holding the fish and kicking the sharks away with my flippers. I had worked so hard to catch it, so I didn't want to give it to the sharks, and I thought it would be ok if I lost an arm or a leg. When I got on the boat to pull the fish up, a column of black water shot up from the sea, and the next moment, the fish had disappeared. The shark had snatched it from me. I decided to get revenge, so I went back into the water, but the sharks were so powerful that I quickly came to my senses (laughs)."
A few days before the interview, I harpooned a huge dogtooth tuna. After about 30 minutes of tug-of-war underwater, the fish went limp and lost all strength. It was only 5m from the surface. As I tried to pull its massive body up, the fish, with its last bit of strength, tore off the flesh and skin where the harpoon had pierced it and escaped. What happened next was surprising.
"Normally, it would have fled to the bottom of the sea as fast as it could, but instead it came back right below me. It glared at me with its huge eyes the size of a clenched fist, and slowly disappeared into the sea. Its internal organs were ripped to shreds, and it must have been on the verge of death. Perhaps at the very end, it came back to see the face of the thing that had tormented it. That fish is quite an incredible fish."
Every time he faced a giant fish, he felt that "something was missing in me." The tremendous force transmitted through the rope. Kosaka describes this sensation as "the fish's life-risking retaliation against me."
"I dive barefoot into rapids that feel like I'm in a washing machine, and confront fish with just a harpoon. The fear of being dragged underwater or attacked by a shark never goes away. But it's an experience of being treated equally by nature as a 'bare life.' Just like the fish that glared at me, I want to see the true nature of nature, which can only be seen when life is at odds with life. That's all there is to it."
Three weeks after the interview, I received an email from Kosaka saying that he had caught a 105.5kg dogtooth tuna. He didn't go into details, but he did include the following:
"Right now, my passion for dogtooth tuna is burning stronger than ever. This may just be the starting line."
Dogtooth tuna are classified as fish similar to mackerel and bonito. They migrate along coastal areas facing the open ocean. Because of their sharp, canine-like teeth, they are called "Dogtooth Tuna" in English-speaking countries and "Devil Fish" in Africa. 
The caught dogtooth tuna are butchered and the meat is eaten by the group and distributed to local people. It is also sometimes salted and preserved for long periods of time.
A journey to experience Kosaka's adventure
Yoron Island, located between Kyushu and the main island of Okinawa, is also known as the "Pearl of the Orient" due to its white sand beaches and crystal clear waters. Its unique culture, a fusion of Satsuma and Ryukyu, is also appealing. "It's amazing that even though it's an inhabited island, the coral is healthy and the water is so clear. It's amazing that you can dive in such beautiful waters, even though the access isn't that bad!" (Kosaka)
