The Holy Grail of Eris, Vol. 4 (light novel) — Kujira Tokiwa

NEW FRIENDS AND OLD SECRETS

Lucia O'Brian is heading to the Republic of Soldita to visit a friend, and Connie, Randolph, and a certain glamorous ghost wind up coming along for the ride. At first, Scarlett doesn't think much of the idea, but that all changes once she learns their destination -- the island of El Sol, where her mother once told her the starry crown of Cornelia Faris lies hidden. But there's more to this treasure hunt than meets the eye and plenty of trouble waiting for Connie and Scarlett across the sea!