So, I was recently reminded about this series, and because of that, I also remembered that Book 4.5 never got a proper translation. Like, I kinda remembered the original translator having an agenda of sorts and just straight-up didn't translate a whole section of the story. And since it seems like no one else has done anything about it, I got tired of waiting and made my own translation in a Google document:

https://docs.google.com/document/d/1YrCtAkuNFdxNR-Ov_ZisXYIs8gqcp6H92mnyAr9Mv7A/edit?usp=drivesdk

Anyone is free to use it for scanlation purposes, but take note: My skills are somewhere between passionate beginner and skilled apprentice. I feel satisfied with my work, but I'm still only about 85% confident in it. You should probably get someone with a firm grasp of the Japanese language to compare my script with the original text before you commit to anything.