(Apologies if I get some bit wrong since I skim through some bits out of disgust :v)
Carol try to get info on how the kids get the pit viper, old man whined.
Then the kids mention something about the orphanage director being quite sick.
Mamari had a strong reaction to that.
Later we learn that Mamari came from this town, in fact from that orphanage.
Mamari ask Carol to save the director.
Carol go and do her thing, and learn that someone came to just give the children the pit viper for free as 'medicine to make you better'
Carol came back, and the next day find Kaid and the mage suffering *coughwithdrawalsymptomcough*
Carol try to give them her medicine, but their throats are too dry to take it
Mamari walk in with the tea
Carol was doubtful,but give them the medicine with tea
more suffering reaction
old man come in, talk trash about how dare Carol think her medicine is a panacea that work on everything, and tell Mamari to just make more of the tea, because THAT is a true panacea
at first the two showed some suffering, but soon falls asleep
old man leave with one last bitching
as Carol wondered aloud what happened to them (since they were like that before she showed up) Mamari started timidly explaining their state (their body couldn't handle the tea's power), and mention they might suffer again
Carol then beg Mamari to say what she knows about those two, because she just want to save them
Mamari then cave and start with saying the tea was made with kodama and monster parts, and the chapter end with her about to go into full confession mode
So my speculation is this:
The old man is the mastermind and the 'goal' for this trip was to actually get Kaid and the mage addicted to pit viper so he can use their withdrawal symptoms to order them around.
And now that Mamari is about to spill the bean, Carol will likely make the antidote
Maybe she'll get captured by the old man either right after feeding them the antidote or right before which leave Mamari to feed them to redeem herself.
The old man will then get a chapter or so to gloat about his evil plan to make all the high ranking people addicted to his drug and subservient to him because otherwise they'll suffer the withdrawal symptom.
Cue Kaid and the mage come in to rescue Carol and also show "yeah, we recorded your confession.....huh this feels deja vu"