Great Void Sea Battle, Imaginary Scramble – To the Surface, Nautilus!
After one last attempt at the gacha (skip to 3:48 if you don’t care about it), the test run continues. Suddenly, Xiang Yu starts behaving strangely, hands femC a couple things, then goes to sleep. A series of strange events ultimately leads to the female Servants wearing swimsuits, and two new Servants joining the party. Specifically Yang Guifei and a mysterious female Vincent van Gogh. Now the Nautilus needs to be piloted through a strange new version of Void Space.
Full game playthrough: https://www.youtube.com/playlist?list=PLBC8w17FA1cv9oe63cGhYEhlaqyQxAl6v
Individual playlists by Singularity/event: https://www.youtube.com/user/pokedude9OO/playlists?view=50&sort=dd&shelf_id=6