In the last scene, why did the tentacle monster say he was going to rape her for three days? If i was him, I would rape her for like 10 years. If I get tired of her, I would pass her to my tentacle friends, share the fun.
Megu is the elderist of the 3 sis, she gets fucked most easily. Because the tentacle master made her to become his bitch long ago, and she was getting hunted by her prey sense then, with every encounter result in a tentacle fest. She is the most powerful sis but she get out numbered by tentacle minions and tormented by her memory. Eventually she had a plan to borrow the main char's (the guy fall in love with Ai) mind to destroy tentacle master and break her self free from his shadow. its in the official plot if you watch the anime. After all the jerking off , I kinda feel some sympathy for her, she was a lonely heroine who fight an up hill battle and win the hard way. She managed to pick herself up after all that shame and submission.