As per the results I have got and research, I have found that there is an issue with PDF style rendering for English with Japanese content.
So finally I found a solution,
- Apply space between the Japanese and English words.
- Iterate the whole string (list with space delimiter)
- Then It is possible to differentiate the English words from the Japanese words by Regular expression
- Apply separate style for English words by wrapping them by span (or any) tag.
I don't know whether this is the proper solution for this issue. This is what I have done for solving the issue.