BrainDojo Developer Interview: A Brain Training Dojo Where Every Day Is Practice

Development of BrainDojo started on June 3, 2024, and version 1.0.0 was released on February 1, 2025. It is a brain training app with handwriting, reading aloud, arithmetic and memory training, available in 16 languages on iPhone and iPad.

The Brain Dojo Check and the stamp calendar arrived in March 2026, the first-time setup and the master’s words in July, and in version 1.7.0 in October every training except the newest ones became free to play. I asked hiroki, who made it, about how it started and how they think about it now. The answers are kept as close to the original Japanese as translation allows.

An app for any spare minute

Q. You started BrainDojo in June 2024. What were you trying to make?

I wanted to make a mobile app like the one it is now, with lots of brain training based on scientific evidence. I made it because I wanted an app myself that let me train anytime, anywhere, whenever I had even a minute to spare.

I am particular about making each training fun to play and effective as training, so there were only a few at first. I kept updating it bit by bit, and now there are close to 50. Each one takes a few minutes, and if you keep doing even three a day, you can make activating your brain a habit. If brain training can become a habit the way strength training does, I think it is good for your quality of life too.

We are entering an age where AI means we don’t have to use our brains, so I think this app will only become more necessary.

Q. The early code had drawing, a pedometer, a balance test, and pages for kana and kanji.

At first I was exploring a lot, so I put in experimental content too. But it became too varied and hard to use as an app, so I narrowed it down to brain training that builds things like focus and memory.

Every day is practice

Q. Why did you choose the word “dojo”?

Because it is based on Zen thinking. The idea that every day is practice. It also means it is made in Morioka, Japan, and I grew up with Zen teachings myself.

Training your brain sounds easy, but keeping it up every day is hard. I am making this app as a place to experience that hardness of keeping at it. I expressed that with the word dojo.

Q. Inside the app it says “Developed in a small studio in Morioka, Japan.” How does making apps in Morioka affect your work and thinking?

Morioka in Iwate is cold in winter. It is the countryside, full of nature, and for better or worse there is nothing here. Compared with places that set trends, like Tokyo or New York, there is nothing. But within that nothingness there is everything. In Zen words, “Originally there is not a single thing; within nothing lies an inexhaustible store.” That is the thinking I make apps for the world with.

Made for family

Q. Do you yourself feel that you can’t stay focused, get distracted, or forget things?

I don’t, but my family does. That is part of why I started making it.

Q. Do you use BrainDojo every day?

Sometimes I do, sometimes I don’t. My family uses it every day.

For me, brain training works almost too well. If I use it every day, my brain gets so active that I lose weight, which is a downside. There is a story that the brain burns a huge number of calories. It might be good for people who want to diet.

Handwriting at the center

Q. The store listing says “handwriting reaches brain areas that tapping can’t.” If you put your reason for insisting on handwriting in terms of your own sense of it, what would you say?

I don’t think there is any other brain training app in the world that does handwriting training besides BrainDojo. Nobody treats it as important, so I think that is where the point of me making it lies.

Q. If handwriting recognition misreads, users get frustrated. Why put handwriting at the center of input anyway?

Handwriting recognition works through machine learning, and that itself is a technology like magic. Handwritten characters vary enormously, so recognizing them at all is hard. Recognizing what everyone writes exactly as they intended, 100% of the time, is a technical challenge and something to work on from here. But even at the current accuracy, with some care it works at a level where there is no problem, so I use it as a core technology.

Measuring and training

Q. The Brain Dojo Check measures three areas, processing speed, inhibition and short-term memory, and returns a rank from 10th kyu to 10th dan. Why three areas, and why a rank instead of a score?

Because making it too complicated makes it hard to understand. The same test doesn’t come up every time, so a rank felt more fitting than a score. It also fits the dojo metaphor.

Q. The Brain Dojo Check is always free, once a day, and doesn’t earn a stamp. What was the thinking behind separating measuring from training so clearly?

Having a cycle of measuring and then training means bringing in a scientific approach. Opinions on the scientific effects of brain training are divided, but I think it is interesting that users can run a cycle of improving their own test results in a scientific way.

Q. In April 2026 you raised the bar for ranks. That means users see a lower rank than before.

I am always reviewing standards like that, including the difficulty of the training. It is something I am always feeling out.

A master, and keeping at it in moderation

Q. The master’s words include many sayings based on Zen phrases, like ichigo ichie and nichinichi kore kōjitsu. Why did you put a master in the app?

Keeping up brain training is hard, so I thought it would be good to have someone like a Zen master. I think it is nice if you naturally learn Zen thinking while using the app.

Q. You put a goal like “3 days a week” ahead of a daily streak. Why doesn’t a habit app push you harder to do it every day?

When doing it every day is the standard for a habit, I felt it was pretty tough. Even keeping at it in moderation, you can feel the effects of brain training. I also came across a scientific paper saying the effects of activating the brain last a lifetime. Continuing is what matters.

Q. In the first-time setup, choosing “3 min,” “5 min” or “10+ min” sets the daily training to 2, 3 or 5. How did you decide on those numbers?

I designed it so it isn’t a burden to keep up every day, but there is still enough load for the training to actually activate the brain.

Q. What do you think decides whether someone can keep doing something?

Ease and a sense of growth. I think people keep doing something when they feel a return that beats their expectations for the cost they put in. So I think brain training being easy, and giving a sense of growth, are both musts.

Who it is for

Q. In May 2026 the Japanese store name changed from one about building a brain training habit with reading aloud, arithmetic, kanji and handwriting to one about focus and memory for adults, and the English name became “ADHD Brain Training.” What led to that?

I reconsidered more strictly whose problem it solves, and what problem. As a result, I thought I should make the concept clear as an app that solves the brain-related worries of working adults. Working adults have many situations, at work and elsewhere, where they can’t afford mistakes. I think an app like this is useful there. I made it so that elementary schoolers and teens can use it too, so it isn’t something only adults can use.

Q. You use the word ADHD. Where do you draw the line?

I don’t guarantee any treatment effect, but there were actually users who said, as their own impression, that it helped with ADHD-like symptoms, like getting distracted or being very forgetful. So I wanted people with those worries to use it, and I started putting that front and center.

Q. Brain training always comes with doubts about whether it works. How much do you believe BrainDojo trains the brain?

From my own experience, the experience of people around me, and the experience of users, I think it depends on the content of the training.

Any training that puts load on your muscles, I think we call strength training. And muscles you don’t use eventually go back. There is not much room for scientific debate there. But with the brain, it turns into a scientific debate. I think that is because some people started calling “mini games” that put no load on the brain brain training.

Even if you stop strength training and your muscles waste away, nobody says strength training is pointless. In the same way, brain training is a habit of activating the brain. It is like how people with a habit of reading or jogging are better at those things. It is not that you do brain training and instantly become smart.

In BrainDojo’s case, the theme is habits that people today have stopped doing, like handwriting and reading aloud, so I think you can feel some kind of effect. I think quite a few people find, when they write by hand, that they can no longer remember how a character is written. Just being able to prevent that is already an effect of this app.

From Morioka to the world

Q. About half of users are in Japan, followed by Thailand, Russia, China, the US, France and Taiwan. Why did you want an app that began with Japanese handwriting to reach people in other languages?

At StudyX, I make apps on the assumption that they will be used all over the world. Since I make them for the world, adding languages and localizing content is work I always keep doing. There are differences in language and culture, and some parts are hard, but that is also what makes this work interesting. Being able to make something used around the world from the Japanese countryside is something only this era allows.

Q. The README says “No marketing for at least one year.”

I think a policy of putting improving the app’s quality above everything else is important. When you release an app, you tend to expect lots of people to use it even if you do nothing. But in reality, you keep improving it for a long, long time after that, and only then do users who keep using it gradually appear. Launch first, watch how users react, and focus on raising the app’s quality dramatically. That is still my stance today.

Ads and tips

Q. In 1.7.0, you made every training except the newest ones free with ads, and put the new ones in Plus. Until then the landing page said “Neither plan shows ads.”

Personally I dislike ads, and I had a policy of not using them in any of my apps. But with a nearly endless choice of apps, even getting people to try one has become hard. And I learned that most people don’t dislike ads that much. If they are not excessive, people accept them.

So my thinking became: people who don’t mind ads can keep using it for free to a fair extent, and people who want to remove ads can pay. I really want lots of people around the world to use this app, so I made that change to reach more users.

Q. Besides sharing, reviews and subscribing, you offer a ¥150 tip as a way to support development.

I tried it as an experiment. Japan has no tipping culture, but places like the US do, so I put it in to see how it goes.

As more people make apps with AI, I think something like a human touch, what thinking an app is made with, is going to matter more. At least I myself want to know what kind of person made something. From now on I want to actively share who I am and what I am thinking as I make things.

What comes next

Q. You keep making many apps. Where does BrainDojo sit among them?

I make the apps alone. I have had help creating some content and assets, but basically I design, develop and keep updating everything myself.

I feel BrainDojo has big potential, so I want to keep raising its quality. I am also developing BrainDojo Kids, a version for children, so I will keep improving quality across the BrainDojo series.

Q. You added 16 new trainings in October 2026 alone. What do you want to add from here, and what have you decided never to add?

I actually make the training based on scientific evidence. I will keep making training, and I will release sister apps as part of the series. What I will never add is low-quality content with no evidence behind it. I will only do what is useful to users.

Q. How far would you like BrainDojo to go in the future?

Medicine is a legally sensitive area, so it would be interesting to verify, with researchers at medical schools and the like, whether it has a medical effect. It would be good to develop a medical device based on BrainDojo’s training that medical institutions could use. If somewhere is interested, I think that kind of direction is possible.

Q. Is there anything you want to say to people who haven’t tried BrainDojo, especially people who blame themselves for not being able to focus?

Please give it a try once.

About BrainDojo

BrainDojo has 40+ trainings covering handwriting, reading aloud, arithmetic, memory and attention. Today’s Training is picked for you every day, and when you finish, you press a stamp on the calendar. The Brain Dojo Check runs once a day, measures processing speed, inhibition and short-term memory, and returns your result as a rank. Every training except the newest ones is free to play, and BrainDojo Plus removes ads and lets you play the new trainings anytime.

For a first session, see Getting Started with BrainDojo. For the plans, see BrainDojo Free vs Plus, and for the research on brain training, see Does Brain Training Work? The app itself is described on the BrainDojo page.