Nintendo's DS brain training games – Dr Kawashima's Brain Training and More Brain Training from Dr Kawashima – have sold millions worldwide. As a result, you might think that'd leave the elusive Dr Kawashima training his own brain by working out where to distribute all his billions of yen: fast cars, fast women, fast interest and so on.
But not so, because according to an interview with the man himself by news site AFP, he's chosen not to take a single yen, preferring instead to work for a living.
"Everyone in my family is mad at me but I tell them that if they want money, go out and earn it," says the 48-year-old professor using the sort of infuriatingly sound logic that would force you start plotting his mysterious demise were he your own parent and you a (worryingly disturbed) adolescent.
Royalties from the Brain Training games have now reached ¥2.4 billion (around £11 million) since the debut of the first game in 2005. Under the rules of his employer, the state-funded Tahoku University, Kawashima could take half of these proceeds for himself while the other half would go to the school. But instead he has poured his own half into funding research into ageing and cancer and is happy to live off an annual salary of around £50k. Which is admirable.
Speaking of his video game-starring status, the man says he always "wanted to put my brain in a computer so it would be around to see the last day of humanity".
However, he only lets his four sons play video games for one hour at the weekend and once snapped a game disc in half when they broke the rules.
"What is scary about games is that you can kill as many hours as you want. I don't think playing games is bad in itself but it makes children unable to do what they should do such as study and communication with the family," he says.
He also doesn't use his own software to keep his own brain nimble as he's confident his research work is enough. To be fair, if you've been spending the afternoon head deep in neuroimaging, answering '6 + 1 =' sums against a clock probably isn't all that challenging.
The interview ends with Kawashima apparently saying with a smile: "I'm confident I'll go senile. Researchers, especially those in medical fields, are said to die of what they are studying. Since I've been studying the brain, I'll die of a brain disease."
Nintendo is probably hoping he doesn't – just think of the negative publicity.