@Grishnag No, look up the history for the device. It was created for "dirty" stuff, but because we are talking about the 60's it was marketed as a "shoulder massage device" to A.) Be able to advertise the device B.) hide the intended use from nosy husbands. Might be considered an early version of viral marketing because it basically required housewives talking among themselves about it for its private usage to become popular.
I think Hitachi now claims that it was originally developed for "Health Care" but even in the wiki you read about them celebrating an old sex shop (good vibrations) anniversary.
every chapter where I have to experience this obnoxious pseudo-NTR lowers my enjoyment of the series. just let me enjoy some fluffy Nanako/Eiji progress, I don't give a fuck about worthless cliche drama that I already have to put up with in every other goddamn romcom manga.