The fifth volume’s title is now added in the ToC page. It’s the same as the chapter title. I didn’t add it before since it’s such a huge spoiler.
On other news, more information about the manga has surfaced. It’ll begin in March. If I’m not mistaken, chapters will be released first in the website I’ll link. Also, it’ll be drawn by Yoshikawa, Hideaki-sensei (吉川英朗先生).
Here is the LINK. Just scroll down. It’s in Japanese though.
For those that don’t want to click on the link, here’s the image that’s in the page