And what next struggle or get digested.
Ok found out by myself and I am now at floor 10 and holy shit do you get completly get frown left and right
To feed the ghosts, you need the endosomatic heart (because letting yourself be digested to death when you're looking for someone is stupid).
It's the red melting heart you might find in stores at the beginning of each floor. (you can try reloading to get the item you want)
Once you do, you can allow yourself to be digested by most spirits until the struggle gauge turns into a pink melting heart.
The ghost will allow you to struggle free and drop items, along with some dialogue and a ghotiary entry. Kamnspi might befriend you without the heart, I'm not sure.
There are some exceptions to the rule;
Nahara and possibly Boobloomi (because of a glitch to where befriending her will get you an instant game over)
Mitsuro and Honeyghast (because they are bosses, and they can't even be eaten)
Jellotin (I mean, it works, but the ghostiary implies that Jellotin will transport you somewhere else in the future.)
SPOILERS
....something. (because it's possibly the main antagonist and is pure evil. Japes hates it and wants to kill it.)