@xiaotiao
If you have the raw, meaning the text bubbles are still in Japanese, here's what you can do;
1. Go to https://sourceforge.net/projects/capture2text/files/Capture2Text/ , get latest version (assuming you're on Windows, no need to install it)
2. Launch by clicking Capture2Text.exe in its folder where you extracted it.
3. In tray right-click its icon, go to 'OCR Language', choose 'Japanese', make sure 'Show Popup Window' is enabled
4. Go to a site with raw manga/open raw manga file
5. Place mouse pointer at top-left of text in a bubble, and click Windows Key + Q (default), drag the resulting blue box so the whole text is contained, press Windows Key + Q again
6. The resulting text should appear in the popup window (if you can't see it, it's usually in the top-left corner of your screen, or you don't have it enabled), copy it(it's probably already copied to your clipboard)
7. Go to DeepL (https://www.deepl.com/translator ), paste the text in the box and translate from Japanese to English, now it's translated (you could use google translate, but deepl usually gives better results)
For further issues or if you didn't get the above, consult this page; http://capture2text.sourceforge.net/#standard_ocr_capture
No idea if that'll be any more accurate than copying from the novel though, perhaps you can combine the approaches...