Amakusa Reveals Avicebron's Name

“Yes, Avicebron – I wish to propose your surrender.”

Shirou revealed Caster’s true name without any fanfare – but that no longer came as a shock to any of them. While Shirou did not possess Command Spells against the participating Servants of this Grail War, as a Ruler, he still possessed the ability to discern the true names of every Servant present.

- Vol 3 Chapter 1