The rest of the chapters can be found:
https://ww7.mangakakalot.tv/manga/manga-lj988618
The uploader put it by its stage and part, rather than volume, which is why it says volume 45, although there are 20 volumes.
The site seems to be inacessable.
Nm, the site is accessible, but the series was delisted
Nm, the series is getting reprinted by 7 Seas Entertainment & it will include the digital-only issues.
Currently, it is complete, but at 20, TWENTY, volumes... (⊙…⊙ ) not 15.
If someone could complete it, thank you so much... (づ￣ ³￣)づ