I was looking at the Wikipedia article for Detective Pikachu (名探偵ピカチュウ) and stumbled upon this information.
Until May 15 2018 you can get a free short story called 名探偵ピカチュウ ～第０章イーブイからの依頼 (Detective Pikachu Chapter 0 - Request from Eevee) for free for your Kindle or a device with a Kindle app.
To do this you must have an account for amazon.co.jp with a Japanese adress. Since it’s only digital media, the physical adress doesn’t matter, you will get it to your device anyway. I tried with an account where my real outside Japan adress is used, and it wouldn’t let me download it.
I also assume you will be able to keep reading it after the 15th, as long as you’ve downloaded it before that date.
I read a little bit of it on my iPad. It’s not terribly hard, but I absolutely did not know all the vocabulary in it like:
出くわす - to happen to meet; to come across
山ほど - a heap; great amount of
レンガ - brick (as in material for building houses)
Feel free to laugh at my limited vocabulary
And have fun reading!