Hi Masamune! Looked into it: you're a Dawn Warrior, and in v83 Dawn Warrior Brandish tops out at 20 — the level Kiku's Drill Hall training teaches. Cygnus Knights have no 4th-job advancement, so there is no Brandish 30 for them; the level-30 book Abdula sells is the Hero's own, which is why it says Hero. Whether Dawn Warriors should get a way to 30 here is a decision for the owner, so I'm leaving this open until he decides.

Good news, Masamune! Abdula's Brandish 30 book now works for Dawn Warriors too. Once your Brandish is at level 15 or higher, read it (50% chance; the book is used up either way) to raise its cap to 30, then train it with SP.