I also read Japanese (novels) a lot. If you don't mind using an extension, I recommend Sider [1], so that you can select texts and use the Sider popup to translate it. Custom prompt for translation is also supported. Cons would be that Sider does not support translation history, so you need copy&paste to save it (you can also login instead; I've never done that though).

[1]: https://chrome.google.com/webstore/detail/sider-chatgpt-side...