User blog comment:HighSchoolStoryLover!/Number of diamonds needed to be able to select all diamond choices in all books./@comment-3452092-20180827235028/@comment-33834897-20180828003544

It is based on 1 playthrough only. So only 1 LI unless you can spend on multiple LI at the same time. Also only 1 clothing/hairstyle for any choice (the most expensive one). So in other words, the max diamonds that you can spend on 1 playthrough.