not sure about missing people
Not sure about missing people, the only quest I remember about missing something is the minister magic sissors and it can be craft using parts drop by zombie in the First Quest Tower Basement (assess with the downstair on the top left corner of the ground floor.
Forest of Witch is a quest limit to use MC and Shiro only, the entrance is the big forest in the left of the overworld map, a wierd mushroom will block you right away and it is unkillable, you gotta "Run Away" to proceed. Next step is pretty obvious. After done step 2, talk with the NPC in the wood cabin to get hint how to navigate though the loop.
The hunting ground is wierd, the only quest it related to is having a new harpie in there and you are surpose to catch it with a perfume or something acquire from god know who because I somehow catch it without the perfume and get it latter.
Vampire is a pain in the arse, the route down south has a shadowy castle and interact with the smoke will start it. It's a solo mission so grind your Sythe girl Dorithy. She gonna wake up in a dungeone and you have to get essence of 7 sins to battle the boss. 2 sins, Pride and Guttony, will be complete for free if you endulge in it, the rest are miniboss battles (counter spell skill is your friend), lust is the two coffins just incase you cant find them, ya gotta clear 5 sins first to fight Lust and then Envy. Boss gonna give you hair loss. Dude summon 4 minions and will eat them each turn, even at the first turn, if he able to eat all of them, he turn supper saiyan, you ded, otherwise, he is a fuckin stat stick and you have to pray he doesn't use blood suck twice a row and one bang you, it's physical damage so you can't counter spell it.