This must be Scintilla's issue because Notepad++ has the same problem. See if this can be localized and reported to them.
Normally, if a line wraps (line wrapping must be enabled - Ctrl+W) pressing End puts the caret to the end of the current subline or (next End) - to the end of the line. So no matter how many sublines a line is wrapped to, pressing End twice will put the caret to the end.
Same with Home and with Shift+Home/End.
However, if a line consists of Japanese symbols - Home/End navigate to the preceding/following subline. So a long wrapped line will need Home/End pressed multiple times, not just 2. Is this intentional and if so then why/what for?
For tests you can create a long line by copy/pasting the following two symbols: 日本