This is the official Samsung Galaxy A21 (SC-42A) user manual in Japanese provided by the manufacture.
The Galaxy A21 with model number SC-42A is now available from NTT DoCoMo – A mobile phone operator in Japan
The model name for NTT Docomo Galaxy A21 is SC-42A. It is a variant of the Galaxy A21 designed for the Japanese Market.
From the below link, You can download the NTT Docomo Galaxy A21 User manual in Japanese. Sadly, The English version user manual for Docomo Galaxy A21 is not available.
File Format: PDF
You may need an Adobe Acrobat Reader to open the NTT Docomo Galaxy A21 User manual in digital PDF.
Need more help? please visit samsung.com/jp, Samsung Japan’s official website. and here you can find Docomo Galaxy A21 Specs & features in detail.