These days, Espressif has seen two new books on ESP8266 in Japanese language available on Amazon written by Buinsanngo. Here’s a brief introduction of the two books:

Beginning IoT Programming with ESP8266 (Kindle Edition)

This manual describes the basis for building a wireless IoT system in ESP-WROOM-02 single Wi-Fi module.

Buy this book here on Amazon.

Beginning IoT Programming with Arduino and ESP8266 (Kindle Edition)

This book explains the basis for establishing a wireless IoT system using the ESP8266 and Arduino.

Buy this book here on Amazon.

Espressif highly appreciates the efforts of developers like Buinsanngo to share their experience and knowledge with other ESP8266 lovers around the world.