
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.

ok im ok with adding rape to the story in fact it makes sense to do so in this scenario but her attitide the next morning? really? this is trash man? also the art of the cover is misleading aint no where on that level

it makes more sense in the novel. She doesn't actually like him ore anything, but she needs to get on his good side because she is afraid he will kill her (remember he is a bandit). She is using her cooking knowledge to gain the trust of her captors so that she will be treated better and can have chance to make her escape. Although she does start liking him a bit, she doesn't actually fall in love with him for a looong time
spoilers....
she runs away and escapes from him when she has the chance, and it takes him a long time to find her again, and a lot of grovelling before she forgives him.
kinda glad that he was thwarted by a slime if he was beyond op it gets boring and cliché