The archive · Product Ideas · Product decision · 2019–2022
Tuna Scope: Dentsu trains AI to grade tuna with a master artisan's eye
An AI trained on 4,000+ tuna tail cross-sections inherits a Japanese artisan's ten-year skill in one month — and buys tuna remotely during COVID.
Dentsu Inc. · Sojitz Corporation · Kura Sushi
What it had to solve
Kura Sushi, Japan's largest conveyor-belt sushi chain, bought tuna through master merchants who judged quality from the cut of the tail — a skill said to take ten years to learn and impossible to verbalize. Pandemic travel restrictions stopped artisans from flying to ports in Japan and abroad to pick fish, threatening supply.
How it works
Kura Sushi, Japan's largest conveyor-belt sushi chain, had always bought tuna through master merchants who judged a fish by the cross-section of its tail — color, sheen, firmness, the layering of fat. The skill is said to take at least ten years to acquire, and the masters themselves cannot fully explain how they do it. When COVID-19 travel restrictions stopped artisans from flying to fishing ports, Kura Sushi's purchasing model broke.
Dentsu creative director Kazuhiro Shimura had been mulling the idea since watching Toyosu wholesalers at work: could an artisan's tacit eye be taught to AI? With ISID and Sojitz, Dentsu photographed the tail cross-sections of more than 4,000 yellowfin tuna on smartphones, paired each image with a master's five-level grade, and trained a deep-learning app. In about one month the AI matched a 35-year veteran's judgement roughly 85% of the time.
In a world first, Kura Sushi used the app to buy tuna remotely in Dalian, China, and sold the AI-selected fish as 'AI Tuna' at 461 restaurants. Sales ran about three times higher than usual during the pandemic; earlier trials saw about 1,000 plates sell out in five days, with roughly 90% of tasters rating the AI-picked tuna tastier than same-priced alternatives.
The project won a Silver at the 59th ACC Tokyo Creativity Awards and the Spikes Asia 2022 Creative Data Grand Prix, earned coverage in 1,500+ outlets across 57 countries, and was adopted by Japan's Fisheries Agency as an export program. Tuna Scope-certified fish went on sale in New York, Singapore and Tokyo.
Why it lands
- The insight was that the skill was tacit: masters could judge tuna but could not verbalize how, so the only way to preserve it was to let machine learning absorb the evaluations themselves.
- Data sourcing was itself the creative solution: instead of interviewing masters, Dentsu partnered with trading house Sojitz to photograph over 4,000 real tuna tail cross-sections with smartphones.
- The pandemic turned a nice-to-have into a necessity: with artisans unable to travel, AI remote purchasing was the only way to keep supply flowing, so the constraint made the idea adoption-ready.
- It reframed AI from 'replacing jobs' to 'inheriting a legacy', which gave the story cultural weight in Japan and abroad — hence 1,500+ media mentions.
What it did
AI-rated tuna sold at roughly three times the usual rate during the pandemic, and the project drew coverage from 1,500+ outlets in 57 countries. Earlier, 'AI Tuna' sold out about 1,000 plates in five days at a Tokyo counter, with roughly 90% of tasters rating it better than same-priced tuna. It won a Silver at the 59th ACC Tokyo Creativity Awards and the Spikes Asia 2022 Creative Data Grand Prix, and Japan's Fisheries Agency adopted a Tuna Scope export project for New York and Singapore.
What you can take
When a dying craft's judgement is tacit and unverbalizable, capture it as data: train AI on real expert evaluations, then let anyone use the skill. The same move preserves other fading trades.
Since then
Tuna Scope became a model for preserving artisan skills: Dentsu positioned it as the first AI to acquire a professional skill, and Japan's Fisheries Agency certified an export project that shipped AI-assessed tuna to New York and Singapore. Dentsu says it plans to apply the same technique to other fading crafts beyond fisheries. The app and certification mark remain the brand under which AI-selected tuna is sold around the world.
Sources
- Tuna Scope — Dentsu case page
- Developing TUNA SCOPE: Entrusting the Expert's Eye to AI
- Dentsu Live Wins Silver at 59th ACC Tokyo Creativity Awards
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