Inomata Naoki had naturally seen Chen Yu's Black Leather Tome that he never parted from. Back at University of Tokyo, Chen Yu carried that book with him every day, leaving a very deep impression on Inomata Naoki.
At the time, Inomata Naoki merely thought Chen Yu had a strong interest in occultism and had picked up this tome from somewhere, which explained his attachment to it. He never considered delving deeper or even taking a look to see what was written inside.
But now that Chen Yu told Inomata Naoki he gained his immense power entirely from reading that tome, Inomata Naoki inevitably felt anger, regret, and envy in his heart. He inwardly lamented why he hadn't been more curious and taken a glance at Chen Yu's book back then.
Inomata Naoki couldn't help but muse that, given their relationship, he should have been able to borrow Chen Yu's book to read back then. If he had gained even a trace of insight from it, he might have grown stronger by now.
