Charles wasn't particularly afraid of Julian, having crossed hands with him before without coming to any harm. However, this time, while practicing gunmanship with Julian, he belatedly realized that Byron's youngest Transcendent had a truly fearsome mastery over the spear.
Julian's gunmanship was even superior to Cyrus's.
The same ordinary move, when executed by Cyrus, Charles could handle, but when Julian used it, he could not resist. Apart from his lack of skill in gunmanship, one could also see that Julian's moves were much smoother.
Julian was simply too young, only a freshman. If he reached Cyrus's age, his strength would certainly surpass Cyrus's.
Under Julian's guidance, Charles's gunmanship… still improved extremely slowly.
The Cat's Mask could only extract skills, not special abilities. Not giving up hope, Charles tried once, but only managed to extract "Wine Tasting" from Julian, which was of no value to him.