Tentacles decides to tire them out.

Holding the fully-nude sisters aloft within the safe confines of his den, the octopus Grimm took a moment to enjoy and revel in his victory. It wasn't very often that he manages to catch two victims at the same time, as he only has so many limbs at his disposal for restraining his targets, but he had been steadily growing stronger over the years. Rather than thirsting for the more common negative emotions like other Grimm do, Tentacles thrives solely on the embarrassment, shame, and humiliation of the female gender. It has made him stronger, smarter, and more powerful than one could ever imagine, and the humiliation of these two girls would allow him to ascend even further! But in order to make the most of his prey's embarrassment, he would need preparation. Firstly, he needed to tire them out to drain any remaining strength they had to resist him.

And he knew just how to go about that~.

"K-kyaah! Where do you think you're putting that?!" Ruby cried in alarm as a tentacle slid up her inner-thigh and brushed against her crotch. "S-stay away from there!"

Tentacles understood the girls fear, as he was well aware of how those Mistralian cartoons liked to stereotype his kind as unrepentant rapists. However, that wasn't the case. Tentacles desires embarrassment, not fear, so he had no intention of going all the way with the girls. Besides, he holds himself as being a proper gentleman with standards that he adheres to. Never would he think of deflowering his victims. Instead, his tentacle slowly slid over the younger siblings slit, pressing against it ever so gently that her outer-lips began to part.

"Aah~! Not there! That p-place is sensitive!"

"Get your tentacles off my little sis, you molesting sicko!" Yang roared in anger as she tried -albeit in vain- to struggle free from Tentacles' grip.

Deciding to give the blonde a bit of attention as well, the Grimm raised one of it's limbs that Yang didn't see and approached her from behind. The elder sister was completely unaware of the tentacle mere inches away from groping her ass. Seething in rage as she watched Tentacles fondle her sisters breasts with another limb, Yang elicited a high-pitched shriek as the tentacle slid between her buttocks and began a flossing motion as the tip of limb glided down from the peak of her butt-crack, in-between her cheeks, gently brushed against her asshole, and came to a halt when it neared the bottom of her groin, only to reverse the motion and repeat.

"Get out of there, you pervert!"

"Yang! Ah~! What's wrong?!" Ruby cried in worry, unable to see what what was happening to her sister.

"This thing is -ngh!- wiping its tentacle between my ass!" she answered before resuming her struggles. "Knock it off!"

Any further concern Ruby had for her sister was quickly forgotten as a pair of suction-cups attached themselves to her nipples and began to pull.

"Don't pull on them!"

The fondling continued for a few minutes as Tentacles slowly brought the duo closer to climax. As they neared their peak, he decided to take it up a notch. Seeing as how Ruby had remained docile for the most part, he would give her a bit of a treat as a reward. Yang on the other hand, had been nothing short of a pain in the ass for the entire duration, so he saw fit to return the favor.

Tentacles pulled back the clitoral-hood of Ruby's pussy, and pressed a suction-cup against the teens clitoris. He then began to to perform gyrating motions.

Yang was less fortunate in her 'final stretch', as Tentacles spread apart her buttocks, providing a clear view of the blondes anus. While Tentacles had no desire to partake in vaginal ****, slipping a tentacle up the girls ass was still an option.

As if knowing what it had planned for her, Yang mustered up what little energy she had left in order to fight back. "Don't you even fucking think about it! Keep your filthy tentacles away from my aAAAAAAAASSSSSSSS!!!"

"Oh god~! It's coming~!" Ruby cried out as a wave of pleasure engulfed her body. "AAAAAHHHH~!"

"I -ah!- am -ah!- going to -ah!- kill you!" Yang shouted as she similarly attained orgasm. "HYAAAAHH~!"