BertJapanese
Overview
The BERT models trained on Japanese text.
There are models with two different tokenization methods:

Tokenize with MeCab and WordPiece. This requires some extra dependencies, fugashi which is a wrapper around MeCab.
Tokenize into characters.

To use MecabTokenizer, you should pip install transformers["ja"] (or pip install -e .["ja"] if you install
from source) to install dependencies.
See details on cl-tohoku repository.
Example of using a model with MeCab and WordPiece tokenization:
thon

import torch
from transformers import AutoModel, AutoTokenizer
bertjapanese = AutoModel.from_pretrained("cl-tohoku/bert-base-japanese")
tokenizer = AutoTokenizer.from_pretrained("cl-tohoku/bert-base-japanese")
Input Japanese Text
line = "吾輩は猫である。"
inputs = tokenizer(line, return_tensors="pt")
print(tokenizer.decode(inputs["input_ids"][0]))
[CLS] 吾輩 は 猫 で ある 。 [SEP]
outputs = bertjapanese(**inputs)

Example of using a model with Character tokenization:
thon

bertjapanese = AutoModel.from_pretrained("cl-tohoku/bert-base-japanese-char")
tokenizer = AutoTokenizer.from_pretrained("cl-tohoku/bert-base-japanese-char")
Input Japanese Text
line = "吾輩は猫である。"
inputs = tokenizer(line, return_tensors="pt")
print(tokenizer.decode(inputs["input_ids"][0]))
[CLS] 吾 輩 は 猫 で あ る 。 [SEP]
outputs = bertjapanese(**inputs)

This model was contributed by cl-tohoku.
 
This implementation is the same as BERT, except for tokenization method. Refer to BERT documentation for 
API reference information.  

BertJapaneseTokenizer
[[autodoc]] BertJapaneseTokenizer