Now its Blake's turn – and do pardon me if I borrow the 'heat' trope, but I do think that it might enhance the experience…
Blake supposed that she could have helped Ruby with Port's boxes, and on any other day, she probably would have. Unfortunately, when Blake had woken up that morning, her panties had been utterly drenched; she'd gone into heat. Sitting through classes had been hell – her whole body tingled at the slightest breeze, and every time she sat down, the feeling of the seat pressing up against her entrance through the thin layer of her black silk panties was almost too much. She'd spent the entire day fighting the urge to touch herself, and even then, by the time Port's class came and went, the fantasy she'd indulged in to drown out the man's lecture – involving her burying her face in Yang's glorious, heaving bosoms whilst taking it both ways from Jaune and Ren – had left her panties wet again. So, after getting out of class she'd immediately made for the most remote corner of the library and the coziest armchair she could find; a girl had needs after all – especially a girl in her heat cycle…
Thus had it been that Blake had chosen to curl up with Ninjas of love where no one was likely to find her so she could privately play at being a very naughty kitty. As she reached down under her skirt to stroke the wetness between her legs, Blake imagined herself in the place of her 'novel's' lead heroine, whose first scene involved her introduction as the evil warlord's favorite concubine, and whose subsequent rescue resulted in her then having sex with the hero, before then using er feminine whiles to seduce a virginal shrine priestess into divulging the secret to forging an enchanted sword (which incidentally involved still more sex) but she could only pleasure herself so much.
Setting the book down, she turned around and straddled the thick arm of the chair, letting her full weight rest on the arm. She gasped, clinging to the arm of the chair as she started to grind herself against the armrest, unable to hold back anymore. Working her pelvis side to side on the arm of the chair she moaned, completely oblivious to the tentacles that had begun working their way out of the vent on the floor behind her chair. She was so horny that it hurt, and desperate enough for relief that she'd submit herself to pretty much anyone who came along at that point, or indeed, anything.
It was just then that the first tentacle had worked its way through the seat of the sofa, and finding Blake's calf, swiftly wrapped around it and abruptly heaved her leg upward so that her heel was resting on top of the chair's headrest. That had caught her notice, but before she could recoil, a second tentacle had bound her other ankle, pinning her in what nearly amounted to a vertical split and forcing her to clutch to the corner of the chair if she didn't want to fall backward.
"W-what is-GAH!" Blake moaned and her body convulsed as two more appendages reached up from between the cushions and caressed her desperate womanhood, slipping under the black fabric of her panties and suddenly ripping them open. She bit her lip in slight disappointment; she didn't know what was doing this to her, and at the moment, she didn't care, she just wanted it to stop teasing her and fuck her stupid.
Blake moaned again as one of the tendrils reached back up and traced her lower lips, "Aaaapaahhh! Come on!" She begged through clenched teeth, "Take me… take me… just TAKE ME already-,"
Blake's lust-addled plea was granted before she could finish its third iteration. Not one, not two, but three tendrils plunged up into her quivering wetness at once, and Blake nearly screamed. Desperately hanging on to the back of the chair with one arm to support herself, with her other, Blake languidly fumbled with the buttons of her uniform's blouse and blazer. Her nipples were pert and erect, practically begging for a share of the pleasure and when her blouse hung open, she simply tore her bra off, glancing lazily down to watch her own breasts bounce and jiggle in time with the thrusts in and out of her pussy. Then she let her free hand trace down from her breasts, over her smooth stomach, and over her hyper-sensitive clit until she could feel the members coursing in an out of her like wet and slippery pistons, each thrust penetrating just a little bit deeper into her warm tightness as her walls squeezed down on the intruding tendrils, as though to milk them for whatever pleasure they were worth, and Blake had reached down just in time to feel herself gush onto the seat of her chair. Unlike her previous teammates though, that was not the end of Blake's experience; her heat cycle had put her body into sexual overdrive, and she wasn't anywhere near satisfied.
As Blake came down slightly from her first orgasm, another tentacle had been working its way behind her with designs on her widely drawn ass, driving deep inside her from behind as her first discharge of juices soaked into the cushion. Blake groaned and her body jerked as the slithering intrusion worked its way deep into her ass, completing her little double-penetration fantasy in a manner most unexpected, if also colossally pleasurable.
It was all too much. Blake's eyes lolled back into her head as she came again, and her grip on the back of the chair slipped, leaving her to fall backward, partially onto the drenched seat of the chair and partially hanging off, her legs still spread wide as she let her upper torso drape down towards the floor, her arms hanging limp to the floor. It was only then that her left leg was allowed to come down from its lofty perch, only to be draped over the opposite arm of the chair, leaving her positioned as though attempting to straddle the back of the armchair, her legs spread wide. Through the transition, the three tendrils plowing her vagina never ceased, even as she felt still another tentacle bind her wrists together on the floor.
Blake came a third time, completely helpless and thoroughly satisfied. A little drool escaped the corner of her mouth, and she drifted off into blissful unconsciousness as the tentacles finished with her, withdrawing from whence they had come only after Blake had lost consciousness in her satiated stupor and slumped to the floor.