Sanjima_Shiryu said:
Joking aside, I think the book is either Patchie's diary or a book written about Patchie's time with her friends (Koa included.)

A prize to you.

[deleted]

A Library Assistant unable to read the books in the library would appear of minimal use.

I bet Meiling just found an entry about Koa.

Kinda obvious who's diary it is now (and Sakuya's and Remilia's setup)

I think it's safe to say the entry on Koakuma will involve lots of kind words from Patchy that will rend Koa's heart to shreds.

Either that or Meiling found "Marisa Dream Chronicle with Illustrations part 72".

...Ah!