This craft essence is currently unavailable on the EN ver.Seaside Luxury is can be purchased from Dead Heat Summer Race! event shop.
Here is a list of servants & CEs that can be obtained for the duration of the Summer 2017 event part 1: Dead Heat Summer Race and part 2: Death Jail Summer Escape.
Rashoumon event (Ibaraki Douji event)
Murder at the Kogetsukan
Inheritance of Glory
Best Servants [★4]: 4 Star Tier List
Anne Bonny & Mary Read (Rider)
Berserker - Craft Essences
Ushiwakamaru
Altria Pendragon (Lily)
Passionlip
Chaldean S.I.U.
Ereshkigal
Arthur Pendragon(Prototype)
Gorgon
Black Holy Grail (The Black Grail)