1日30分睡眠ってほんと？「睡眠が一番大事な仕事」と語る田中渓の快眠メソッド
Following the news of Saint Marc Holdings acquiring udon chain Tsurutontan for 12.8 billion yen, Tanaka Kei (田中圭) breaks down the financials and strategic logic behind the deal. He then turns to the glymphatic system — the brain's active waste-clearance mechanism that fires during deep sleep — to explain why he considers sleep "the most important work." He also lays out his personal sleep method: a seven-hour target, fixed daily wake times, and deliberately tiring both body and brain each day.
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What this episode answers
Why did Saint Marc Holdings pay 12.8 billion yen — more than twice Tsurutontan's annual revenue — to acquire the chain?
The acquisition fits Saint Marc's strategy of aggregating sharp, category-focused dining brands and scaling them globally; after closing underperforming stores and completing back-to-back deals for Katsugyū and Gyūkatsu Motomura, the company nearly tripled operating profit from 2.6 billion to roughly 7 billion yen, making Tsurutontan a natural next addition to that platform.
What was Kato Pleasure Group's reasoning for selling Tsurutontan?
As a family-owned company, Kato Pleasure Group concluded that the brand-building phase was complete and that further scale required a larger operator's logistics and infrastructure, so it monetized the roughly 40-year-old brand for 12.8 billion yen to concentrate resources on its hotel businesses, including the Fufu series and Hanafu Resort.
What is the glymphatic system, and how does it relate to sleep?
The glymphatic system is the brain's dedicated waste-clearance network — in place of lymphatic vessels, cerebrospinal fluid flushes metabolic byproducts from around cells — and it becomes most active during deep non-REM sleep, demonstrating that sleep is active brain maintenance rather than a simple shutdown.
What sleep habits does Tanaka Kei practice?
Tanaka Kei targets seven hours as a rule (eight ideally, six as the hard floor), confirms a 10–20% power drop on poor-sleep days using a bicycle power meter, properly tires both body and brain each day, maintains the same sleep and wake times every day of the week, and manages his sleep environment through light, temperature, caffeine cutoffs, bath timing, and phone avoidance.
Can ordinary people train themselves to become short sleepers?
No: natural short sleepers carry a specific rare genetic mutation and represent only a tiny fraction of the population, and Tanaka Kei states that no established training method exists for ordinary people to significantly reduce their sleep requirement.
The Background Behind Saint Marc HD's 12.8 Billion Yen Acquisition of Tsurutontan
Saint Marc Holdings has acquired Tsurutontan, the udon chain operated by Kato Pleasure Group, for 12.8 billion yen. With Tsurutontan's annual revenue reported at around 6 billion yen, a price tag of roughly double annual sales sits at the high end for the restaurant industry. The deal follows Saint Marc HD's earlier acquisitions of Kyoto-based Katsugyū for 11.2 billion yen and Gyūkatsu Motomura for 10.5 billion yen, marking a rapid succession of M&A moves.
The financial results are striking. Revenue that stood at roughly 60 billion yen in 2024 has expanded to nearly 90 billion yen by 2026. Operating profit has grown approximately threefold, from 2.6 billion yen to around 7 billion yen. The company has deliberately shifted its balance sheet posture: its equity ratio has moved from a conservative 60% to 40%, and its net debt-to-equity ratio has risen from 0.2x to 0.75x — a conscious pivot toward leveraged growth. Alongside the acquisitions, underperforming stores have been closed, lifting per-store monthly revenue to 130% of 2020 levels.
The strategic logic centers on building a portfolio of sharp, category-focused brands. Fresh-pasta specialist Kamakura Pasta, Gyūkatsu Motomura, and now Tsurutontan each dominate a single culinary niche. Scaling these specialists globally is the growth thesis the equity market has rewarded, with the stock trading at roughly 18x earnings.
The Seller's Rationale: Kato Pleasure Group's Decision
Kato Pleasure Group is a family-owned company with roughly 5,000 employees group-wide, operating properties that include the luxury Fufu hotel chain and Hanafu Resort in Okinawa. For Kato, Tsurutontan had completed its brand-building phase; growing it further would require the logistics and infrastructure of a much larger operator. The decision was to monetize the roughly 40-year-old brand for 12.8 billion yen in cash and redirect those resources into the hotel business.
Tsurutontan and Tanaka Kei's Personal History
Tsurutontan opened its first Tokyo location in Roppongi in 2005. Tanaka Kei (田中圭) began frequenting the restaurant around the time he joined Goldman Sachs in 2007, and he always ordered three servings of noodles — the chain offered free refills up to three portions, and he never left them on the table. Out of a 58-item menu, he recalls eating the mentaiko cream udon almost exclusively, while being struck by how novel the broader lineup was for the era: beef tendon curry udon, motsuni stew udon, and tantanmen-style udon were all unusual takes at the time.
The Glymphatic System: The Brain Cleans Itself While You Sleep
The glymphatic system, covered in the Nikkei Shimbun, is the brain's dedicated waste-clearance mechanism. Unlike other organs, the brain has no lymphatic vessels, so cerebrospinal fluid takes on the job of flushing metabolic byproducts from the spaces around cells and routing them out. This activity intensifies during deep non-REM sleep.
Tanaka Kei compares it to defragmenting a hard drive. Old-style HDDs would gradually fragment data as files were added and deleted, slowing searches and processing. Defragmentation reorganizes everything back into order. The sleeping brain operates similarly: it consolidates and solidifies the day's information, filters out what is no longer needed, and clears waste. This understanding — that sleep is active maintenance, not a simple power-off — is the foundation of Tanaka Kei's conviction that sleep is "the most important work."
Tanaka Kei's Sleep Method
His baseline rule: seven hours as a principle, eight hours if possible, six hours as the non-negotiable floor. He tracks daily condition with a bicycle power meter and has confirmed firsthand that poor sleep translates to a 10–20% drop in power output.
Three practices drive his sleep quality. First, **properly tire both body and brain during the day**. Routine tasks alone do not fatigue the brain; engaging with open-ended problems and complex thinking produces the mental exhaustion that leads to deep sleep. He cites the tiredness he feels after recording the radio show as a prime example. Second, **keep the same sleep and wake times every day**. Sleeping in on weekends creates "social jet lag" — a misalignment between the body clock and the social schedule — that disrupts the internal clock for the entire week. Third, **environment design**: managing light, sound, temperature, humidity, and mattress quality; cutting caffeine before bed; timing baths correctly; and avoiding phones and work email in the lead-up to sleep.
On short sleepers, Tanaka Kei is direct: natural short sleepers carry a specific genetic mutation and represent only a tiny fraction of the population. No established training method exists to significantly reduce sleep requirements for ordinary people. A life of 80 years with eight hours of daily sleep works out to roughly 23 years spent asleep — but the more rational reframe, he concludes, is to invest in the quality of the hours you are awake.
Takeaways
- Saint Marc Holdings nearly tripled operating profit in two years through aggressive M&A of sharp specialist dining brands, with the 12.8 billion yen Tsurutontan acquisition being its latest step in that global scaling strategy.
- The glymphatic system flushes metabolic waste from the brain during deep non-REM sleep, proving that sleep is active brain maintenance — not a passive shutdown.
- The keys to better sleep are properly tiring both body and brain during the day and keeping an identical sleep-wake schedule every day of the week; sleeping in on weekends creates social jet lag and is counterproductive.
This article is edited from a machine transcript of the first 30 minutes of the episode. It is not an official summary — please listen to the episode itself.