"No, no. It's all right." Seimei drops his hand. "I thought his family destroyed it after he died. Perhaps they didn't. Or perhaps from the perspective of the library, that doesn't matter."

It looks like all the materials on Ysalwen's table - other than her notes - are bound books, which the journal would not have been. Japan did not have bound books in the tenth century.

"I'm sure Hiromasa's journal would be a treasure trove for any historian. But to me he is not some historical figure from a bygone era. He was my best friend."

And you don't peek in your best friend's diary, you know?