Qureate's own spin on Vampire Survivor. The gameplay is very similar with each maid having their own stats and attack pattern based on their gun and melee weapon, as well as a special attack that can help to clear the screen in a pinch.

The story is divided in 8 areas with the first seven areas having 4 missions to complete. In each mission you have to last a certain amount of minutes, kill all the enemy waves or kill a boss and enemies drop materials that you can use to buy items in the store or upgrade the maids equipment. Once the game is finished the survival mode is unlocked, which is the same as VS where you have to last 30 minutes (and you can unlock an extra character by playing it once)

Regarding fanservice, the mini-game to de-zombify the maids y very simple and can be skipped if that's not your thing, but you will at least play it once for each maid.