only logical explanation I can think of would be the farfetched "she was actually secretly really into it/him the whole time" but is actually unhinged in some way? idfk ya its weird. She's gotta be crazy somehow
LOL the one in question from the translator is his mom. She used oniichan as relative to the little sister/representative of his place in the household
wait but like... so what if he DIDNT do that... like everyone who didnt happen to have a demigod come riding by... would they just be all fucked? It's not entirely clear how what he did affected the natural cycle