If one thought about it, one would see there wasn't exactly a lot of time to train Sonzei from zero. Well, he had some techniques and got the training from the Glanvie Clan, so he wasn't completely hopeless.
"You are hopeless!" Roan spoke without a care.
Only Sonzei thought he wasn't hopeless, though... Too bad Roan was there to wake him up to reality. "What kind of shit training have you received until now? I will need a miracle to train you to become good enough to beat a true Leviathan."
"However, you are lucky," Roan continued. "This place just so happens to have the miracle you need: Time."