
he drank sake with an aphrodisiac in it but what's the medicine for? I wonder usually in scenarios like this one its to have children or something since they said he would change is this what they meant and is that why they were ok with having a male bride ?

So basically its medicine mixed with aphrodisiac. The medicine is for kataika (marriage inter-species need to drink the medicine so the body of bride can change and later will able to pregnant). In kaede case, since he is male, there need more preparation (ass prep), that is aphrodisiac function, to make it bit painless.
hell if I found me a hot guy who ravaged my nipples and had ears and a tail I wouldn't let him go either
BAHAHA