Regarding the plot, Da Vinci-chan: If I just think of her characteristics and desires, it's the only reasonable conclusion Suzuka Gonzen, about the holy grail: My wish for the Holy Grail? It would be to encounter a wonderful love! Obviously!
Some of the other servants are references of Tokimeki Memorial heroines: Helena - Yuina Himoo (The Mad Scientist ) Hokusai - Ayako Katagiri (The Avant-garde Artist) Chiyome - Rei Ijuin (The Guy(Girl)) Abigail - Miharu Tatebayashi (The Cute Stalker)
Mash is Okura Miyako from TM4, who starts out as your childhood friend wingman that provides you with info on the other girls, but if you trigger her flag, she becomes an yandere. she stops giving you info on other girls (cause you don't need information on other girls now) and is immune to other heroine's bombs.
Every heroine except the culprit is under the effects of Mental Pollution (i.e. acting like a Tokimemo character)
So the moral of the story is: JK Fox should have loaded up Tokimemo Girl's side instead