I think it's pretty clear from the story that MC was binge drinking. If someone has drunk enough to forget everything by the next day, they were obviously far too drunk to give consent. And Landlady-san acknowledges that, saying she shouldn't have had sex with MC-chan when she was in that state. (Even if MC did remember some of it later on, the fact that she forgot about it at all is an indicative of binge drinking).
But like I said before, it's a gray area situation in this case, because MC-chan doesn't seem to consider that abuse. For instance, I've had sex with my ex in a couple of situations where we were both too drunk to care, and none of us ever thought of that as abuse.
I think the thing about alcohol is that it doesn't necessarily imply rape every time, but since people under alcohol lose the ability to withdraw consent, when you have sex with someone in that state, you are admitting the possibility that you may be raping them.
last edited at Jan 19, 2020 9:16PM