To begin with
Secret Map to the Master's Castle
The goal of this book

Chapter 1: Master the Gift Calculation Method

Warm-up_Cherry Calculation: Three Digits + Two Digits
STEP 1_This is the gift mental arithmetic method.
STEP 2_Get familiar with gift mental arithmetic
STEP 3_Reduce the number of □ and calculate it.
STEP 4_Complete the gift mental arithmetic

Column: Teachings Parents Give to Their Children

Chapter 2: Mentally Calculate Addition, Subtraction, and Division

STEP 1_ Try mentally calculating 'a number with three digits or less + a single digit' and 'a number with three digits or less - a single digit'.
Mental arithmetic of two-digit + one-digit numbers
Mental arithmetic of three digits + one digit
Practice adding single-digit numbers
Two-digit-one-digit mental arithmetic
Three-digit to one-digit mental arithmetic
Practice subtracting single-digit numbers
Addition and Subtraction 20 Questions Learned So Far_Test 1
Addition and Subtraction 20 Questions Learned So Far_Test 2

STEP 2_Calculate simple division
What is division?
Division Calculation Method and Problems
Simple Division 20 Questions_Test 1
Simple Division 20 Questions_Test 2

Chapter 3_+ - Do calculations that mix × ÷ and ( )

STEP 1_Usually count from the left
STEP 2_× and ÷ are calculated before + and -
STEP 3_In expressions with parentheses, the part inside the parentheses is calculated first.
STEP 4_Calculate using mental arithmetic and parentheses

The Arena of Showdown_A Challenge to the Master of Calculation
Summary Test 1_Arriving at the entrance to the Master's Castle
Summary Test 2_Challenge the Master's Apprentice
Summary Test 3_Challenge the Master

supplement

Secrets of Gift Calculation 1: Why You Can Calculate Gifts Using Mental Calculation
The Secret of Gift Calculation 2: A Word to Your Parents

Correct answer
Certificate of Merit for the Master of Calculation

The popular Dark Walk series, with cumulative sales of 720,000 copies (Japan)
The Miraculous Four Arithmetic Operations, Following the Miraculous 19-Stage Multiplication

There is a book that has become a hot topic, rising to the 3rd place on the overall bestseller list in Japanese bookstores in the first half of 2023.
This book, which contains the secret of 'anyone who knows the multiplication tables and addition can mentally calculate up to 19 in 5 seconds', is called a 'mental book' and caused a great stir in the Japanese publishing market.
Afterwards, it once again became the center of attention as it was named as the 'Best-Selling Book of 2023' by Japan's largest publishing distributor, Nippon Publishing & Sales.
This is because it is unprecedented for a children's textbook to enter the top 10 of the overall bestseller list.


This book, which broke the prejudice of those who gave up on math and captivated readers of all ages, from elementary school students to middle and high school students, as well as adults in their 20s and 40s and seniors in their 70s, was later published in Korea as “Mental Math Genius: Miraculous 19-Stage Multiplication,” giving domestic readers the novel and enjoyable experience of naturally learning 19-stage multiplication through mental arithmetic.
And in the spring of 2024, the second book, "Mental Calculation Genius: Miracle Arithmetic Operations," which follows "19-Stage Multiplication," will once again be available to readers.
In Japan, it was published in the fall of 2023 and has since easily surpassed 720,000 copies in cumulative sales, continuing to break many records.
Takuya Kosugi, the teacher who made readers fall in love with math with '19-stage multiplication'.
This time, let's experience the world of 'arithmetic operations' that he teaches us.


A fun journey with otters
Discover the secrets of arithmetic operations hidden by a master of calculation.

The greatest strength of this book, like Volume 1, is that it is easy and fun to read.
We begin by reviewing the core content of Volume 1, multiplication problems from 11×11 to 19×19, by mentally solving them without paper or pencil, and then move on to the next step step by step.
It is also known as the ‘Small Step’ learning method.
If you follow along step by step, you will have the special experience of being able to multiply 19 times in your head at some point, and even do mental calculations that mix '+ - × ÷ and ( )' in just 5 seconds, no, 10 seconds.
However, the only difference from Volume 1 is that, in keeping with the original title, “A book that allows elementary school students to mentally calculate 19 × 19 in one day_Master of Calculation,” this time the story takes place in a castle where a master of calculation (達人) lives.
To this end, we created the character 'Otter', also known as the 'Master of Numbers', and had him join us on our journey to become a master of calculation.
If you actively utilize the key hints that Otter gives you whenever things get difficult or tough, you will soon arrive at the entrance to the Master's Castle.
A tightly closed castle, and the master's disciple blocking the gate.
You must defeat him to meet the ultimate goal, the master.
And finally, I met the master.
Although the protagonist has been trained through long practice and effort, if you follow along step by step from the first step, you can win without difficulty.
The moment you win the final battle, you will receive the 'Master of Calculation Certificate' and the arduous and long journey to master the four basic arithmetic operations will come to an end.

From elementary school students to middle and high school students, adults, and seniors
A magical math book that turns everyone into a mental math genius in one day.

It is important to study math consistently every day.
Because there is no better study than becoming familiar with something through repetition.
Moreover, the importance of operations is emphasized regardless of grade level because students cannot advance to the next level without mastering the basic operations of addition, subtraction, multiplication, and division.
In particular, the multiplication tables, the basis of multiplication, are important and useful formulas that can be used throughout one's life once memorized, so it is recommended that you master them through the book's predecessor, "Mental Arithmetic Genius Operation Method Miracle 19-Stage Multiplication."
If you have mastered the previous work, you will enjoy this book, “Mental Calculation Genius: Miracle Arithmetic Operations.”
In fact, after mastering this book, you will be able to perform all of the following calculations:


① Mentally calculate from 11×11 to 19×19 in 5 seconds using the ‘Gift Mental Calculation Method’
② Mental arithmetic of 'number with three digits or less + one digit' and 'number with three digits or less - one digit'
③ Simple division
④ Calculation mixed with + - × ÷ and ( )
⑤ Calculation mixed with + - × ÷ ( ) and ‘gift mental arithmetic’

This book builds children's confidence through fast and accurate calculations without mistakes, and instills a sense of challenge in adults who struggle with math skills or reach for a calculator even for easy problems. It can be enjoyed by people of all ages.
With the math book "Mental Calculation Genius, Miracle Arithmetic Operations" that both mothers and children can enjoy, experience the pleasant feeling of making math, which used to be difficult and burdensome, fun and enjoyable.