User blog comment:Crimson and Darkness/Volume 24 discussion blog/@comment-28626666-20171225001312/@comment-30924344-20171225021128

Vali when he was a child, wrote 3 books of chuunibyou contents so one of them had made up spells he invented. Lavinia managed to keep hold two of them and made copies of them unbeknownst to current Vali and of course finding out she made copies when he desperately wanted to keep them a secret, would show why he has such an embarassed expression in that illustration: Current Vali and Lavinia.