Can you give the link?
Genuine question, where did you find the info that this is 25 chapters long? Because I'm pretty sure those 4 volumes/books (+ a sequel under a slightly different name) are all we have. I mean, this is a doujinshi (self published) porn book so I'd be seriously impressed if the author managed to keep it going for that long
Correcting myself: 6 books, 2 sequels (basically AU extras from what I've seen)
I was basing it on the part where I got to read the free parts it and like there was this table of contents and I saw the parts where it was in Japanese but there was numbers to the side, and just basing it as like this
Ch 21 - 6
Ch 22 - 44
Ch 23 - 78
And so on, soo yeah. I'm not entirely sure if it is true or not but I'm guessing is that Ch 21 - 25 would be Vol. 4.
I just checked, and it seems they are a re-edit/reprint(?) that got... really split into smithereens. If you check volume 3 they managed to break 150 pages into 10 chapters. It's crazy work, but also shows there are new extras added (original raw was 132p)
As a general rule of thumb in doujins you won't have "chapters" because they are written to be solo books – so while some are shorter or longer, like 20 pages or 100+, when it pertains to the story they're still a single chunk. Whether people refer to them as chapters, books or volumes is moreso personal preference.
Case in point, the chinese TL I have seen of volume 4 still has the old summary of "main story + bonus story" which we have seen in chapters available here. DLsite also has the original page counts, so I think these are CMOA exclusive prints? Probably worth it considering the prices are okay, but I can't tell if volumes 5 and 6 will get the same treatment later.
Just went to the raws where you have to buy it and I just found out that there are a total of 25 chapters and I'm guessing if you go for it its a total of 4 volumes. Please please please to the person who can buy, translate, and post it here pleasee. If I could I would but I am currently broke right now and plus I still have school depts that I need to pay soo I still have that to take care of. And I'm still currently a college student and I can't find that much work right now with how busy I am, but pleasee to the person who can, I will forever be grateful to you!