This item provides Servants with a wearable swimsuit.
CCC is filled with relatively outrageous stuff, but implementing this item in CCC is what made me think “Well, we’ve done it now” the most.
Before the release of CCC we revealed information about the game which included stuff about “Caster’s Swimsuit.” The incredible perverseness of this led to an outpouring of players announcing thing like,
“This is only to be expected of Cas-ko seeing as she was the primary sexy character in EXTRA. Honestly this is so lewd that I can’t even look at it straight, but for now I’ll keep stealing peeks of Cas-ko’s under-boob.”
But we should note that Cas-ko’s EXTRA bikini really isn’t worth mentioning.
For all it’s worth, Caster’s revealing swimsuit was simply a bikini with a very small surface area of cloth.
On the other hand, Red Saber’s bikini takes things even further with a Brazilian bikini that is no more than some string.
Saber’s swimsuit was even more aggressively lacking in string coverage until CERO got angry about it. Prior to that the shot from behind made her look stark naked. Truly a ~ situation.
But really the most outrageous swimsuits are worn by the guys. Especially the combination of Archer and the male version of the protagonist (both wearing swimsuits). Their terrible combination has the power to crush all reason even in the most serious of scenes.

Translator’s Notes
  1. ^ CERO is Japan’s content rating board, like the ESRB or PEGI.
Fate/EXTRA Material: Encyclopedia of Fate/EXTRA