Sexy science experiment tests one of Japan’s most persistent pieces of folk wisdom.
Like any country, Japan has its own collection of folk wisdom, with some pieces of oft-repeated advice not really meshing with actual results. For example, eating stretchy mochi at New Year’s, for example, is supposed to grant you a long life, but actually has a pretty good chance of killing you right then and there.
And then there’s Japanese men’s favorite bit of sage knowledge: rubbing a woman’s breasts will make them bigger. Granted, this isn’t something Japanese schools teach in biology or health class, but there’s no shortage of dudes in Japan who’ll insist, usually in hushed tones over beers with the boys, that rubbing a woman’s chest produces a bigger chest to rub, like some kind of perpetual-boob-generating system.
おや?もうお昼か!
— 安田七奈🍵なーちゃ (@nana_yasuda72) December 27, 2018
ひるなーちゃ🙃 pic.twitter.com/CuM7oECAyw
So as part of a New Year’s TV special, broadcaster TV Tokyo teamed up with Japanese bikini model/race queen Nana Yasuda (pictured above) to find out what would happen if the 27-year-old Tokyo native’s breasts were rubbed 10,000 times. The results were revealed as part of a program in which 10,000-repetition experiments were performed in various fields (including Japanese calligraphy strokes and .kendo sword swings), but, obviously, the breast research was of particular interest to viewers.
"ひたすら1万回"見てくださったみなさんありがとうございました☺️
— 安田七奈🍵なーちゃ (@nana_yasuda72) January 1, 2019
私よりもずっとずっと大変だったちなみんと星野さん本当におつかれさまでした‼︎
そして戸瀬先生ありがとうございました❤️#ひたらすら1万回#1万回ハウス pic.twitter.com/1mfH9NlPsh
However, it was determined that random squeezing might be detrimental to Yasuda’s breasts, and so TV Tokyo also enlisted the help of a “breast development counselor,” who devised a multi-motion cycle that began with firmly cupping the underside of Yasuda’s breasts and transitioning to palming and rotating them. A single 10,000-rub session was also deemed too heavy a workload for the model’s chest, and so the complete experiment would take place over the course of 12 days, with Yasuda herself handling the rubbing duties.
今年最後のひるなーちゃ!
— 安田七奈🍵なーちゃ (@nana_yasuda72) December 31, 2018
2019年もよろしくね😚❤️ pic.twitter.com/SvN676qruv
Along the way, Yasuda recorded her perceived changes. At 2,000 rubs, she noticed that her previously stiff shoulders felt much better. Once she hit the half-way point at 5,000 rubs, she said “It feels like my breasts really are getting bigger,” and 1,000 later, at the 6,000-rub mark, she said “My breasts are overflowing from my bra.”
▼ Yasuda’s 2018 Santacos video
ジングルベール🔔ジングルベール🎅🔔💫 pic.twitter.com/SFDIve0xks
— 安田七奈🍵なーちゃ (@nana_yasuda72) December 25, 2018
Once all 10,000 rubs had been administered, it was time to measure Yasuda’s chest, with the before/after being:
● Before 10,000 rubs:
Bust size (top measurement): 81 centimeters (31.9 inches)
Under-bust: 73.5 centimeters
Cup size: D
● After 10,000 rubs
Bust size: 82 centimeters
Under-bust: 68.5 centimeters
Cup size: F
So according to the program, rubbing Yasuda’s chest 10,000 times didn’t just make her bust two cup sizes larger, it altered the shape of her breasts too, adding volume at the top while compacting them at the bottom.
However, it might be a little early to go declaring this a monumental breakthrough in the field of boobology. Remember that the 10,000 rubs were administered over a period of almost two weeks, during which any number of other factors could have been in play, such as increased calorie intake (and the reduced shoulder stiffness Yasuda reported may have just been a muscle-stretching side effect of regularly performing the rubbing motions). So even if Hitosura Ichimankai’s results are legitimate, it’s not a sure thing that it was all the rubbing that produced them.
美容院行ってネイル行って今年の美容納め完了🤩‼️ pic.twitter.com/nwQnG7Z8R5
— 安田七奈🍵なーちゃ (@nana_yasuda72) December 30, 2018
There’s also the fact that proper science requires experiments to be repeated multiple times in order to verify the relationship between cause and effect, though if Yasuda is willing to devote herself to this research, odds are her fans won’t mind a bit.
Source: Shirabee via Nico Nico News via Hachima Kiko
Follow Casey on Twitter, where he’s wondering what sort of licensing process there is to become a “breast development counselor.”

Japanese swimsuit model’s dried fish bikini NFT series sells out, asking prices soar【Photos】
Starbucks Japan releases new My Fruit³ Frappuccino at only 34 stores around the country
The next time you’re feeling stressed out, you could relax on a Pokémon Psyduck chair from Japan
Japanese government says country needs more women’s room toilets to meet modern society’s needs
Train station platform ramen store closes its doors on half a century of history in Tokyo
Cherry blossoms begin blooming in Japan with record-early starts for sakura season
McDonald’s Japan celebrates spring with… a Strawberry Shortcake Pie?!?
Are Japanese convenience store sandwiches scamming us with their fillings?
We asked our Japanese team of writers how they deal with seasonal allergies in Japan
All-you-can-eat Häagen Dazs among 200 other frozen foods at Osaka’s Chin! Suru Restaurant【Pics】
Japanese teen offers to catch purse snatcher for elderly woman, but is actually helping rob her
Studio Ghibli releases Catbus pullback keychain that runs like the anime character
Nine great places to see spring flowers in Japan, as chosen by travelers (with almost no sakura)
Starbucks Japan opens new cafe and art gallery in top Tokyo tourist neighbourhood
Virtual idol Hatsune Miku redesigned with look that adds new elements and brings back old ones
Studio Ghibli adds new Mother’s Day gift sets to its anime collection in Japan
Komachi Shokudo: Japanese mum’s-style cooking for breakfast, lunch and dinner in Tokyo
The top 10 graduation songs in Japan as chosen by current Japanese high school students
Pizza Hut Japan teams up with creator of one of the country’s best kinds of ramen for ramen pizza
Starbucks Japan unveils new sakura cherry blossom collection for hanami season 2026
Starbucks Japan releases new sakura goods and drinkware for cherry blossom season 2026
The 10 most annoying things foreign tourists do on Japanese trains, according to locals
Naruto and Converse team up for new line of shinobi sneakers[Photos]
Starbucks Japan releases first-ever Hinamatsuri Girls’ Day Frappuccino
Japan’s cherry blossom season predicted to start earlier than we’d thought, especially in Tokyo
Starbucks Japan releases a new Cream Puff Frappuccino for a limited time
Survey asks foreign tourists what bothered them in Japan, more than half gave same answer
Japan’s human washing machines will go on sale to general public, demos to be held in Tokyo
Starbucks Japan releases new drinkware and goods for Valentine’s Day
We deeply regret going into this tunnel on our walk in the mountains of Japan
Studio Ghibli releases Kodama forest spirits from Princess Mononoke to light up your home
Japan’s newest Shinkansen has no seats…or passengers [Video]
Major Japanese hotel chain says reservations via overseas booking sites may not be valid
Put sesame oil in your coffee? Japanese maker says it’s the best way to start your day【Taste test】
No more using real katana for tourism activities, Japan’s National Police Agency says