Apparently there is slight incest and was a lot of bonking between the MC and ML when the grow up (maybe as teens) in the novel Rain
Nothing incest. It was pretty common back in the day to teach your younger siblings about sex ED (by showing how to masturbate or how to have sex (mostly using maid)) And we are not sure if they will add that here in manga.
Bro wth happened??? WHAT IS THE SPOILER???