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
5 Star Servants Tier List: Best Servants [5/9 updated!]
FGO Reroll Tier List [5/11 updated!]
Saint Quartz Farming Guide
1-3 Star Servants Tier List
Best Craft Essence: Craft Essence Tier List
Best Servants [★4]: 4 Star Tier List
3rd Singularity: Okeanos
Dive to Blue
Student Council of the Lunar Sea