⁣"Chaldea has detected a Foreigner in the Hawaiian Islands.
To make matters even stranger, Servants have begun to disappear from Chaldea!
Concerned by the seriousness of the situation, Master is dispatched with several Servants as a protection detail. There, a bizarre battle in the tropics erupts.
A summer festival of the Servants, by the Servant, for the Servants... the Servant Summer Festival... is about to begin!"
(Source: AniplexUS)

https://fate-go.us/servant_fest/