Strikethrough is shown as underline or overline in exported PDF with Japanese font

Summary

Strikethrough is shown as underline or overline in exported PDF with Japanese font.

Steps to Reproduce

1. Navigate to Confluence administration > PDF Export Language Support
2. Install Japanese font (c.f. IPA font)
3. Create a page which contains strikethrough
   
4. Export a Confluence page as PDF

Expected Results

The strikethrough is shown as is in the original page or in exported PDF with the default font (Helvetica).
default-font.pdf

Actual Results

Strikethrough is not shown correctly in exported PDF with some types of Japanese fonts.
japanese-font.pdf

Notes

Not only strikethrough on Japanese characters are affected.
If Japanese font is installed on the environment, strikethrough on other languages including English are also affected.

Workaround

There is no workaround at this time.