Rina falls forward, landing on Alex, her hands on his chest. She immediately freezes up, and looks up into his face with wide eyes. "I- I- I'm sorry!" She squawks, blushing even more. Alex just looks down at her with amused eyes. "Sorry for what?" He says with a devilish grin. His hands slide slowly down her back and dip into her shorts. Rina suddenly moans and shudders, and Alex grins wider. Judging by the placement of the bulge in her shorts, Alex was fingering her asshole. "I must say, you have a really nice ass... Might just rival Olivia's." He gives Olivia a cheeky grin before turning back to Rina. "Mm. Nice full, and round. Just the way I like them!" He spanks her ass hard, making her gasp and jerk forwards. Rina looks up at him with a lustful gaze. "Th-thank you...?" She murmurs, thighs shaking as he continues to finger her ass.
He pulls her shorts down with one finger, tossing them off to the side, and Olivia can see that he has three fingers buried in Rina's asshole, probably preparing her for the impending knot. "Go on... Put them in by yourself!" Alex murmurs, pressing a finger under Rina's chin and pressing it upwards, leaving her no choice to look into his eyes. Rina awkwardly fumbles around behind herself, and grips his dicks, pressing both of them to her ass and pussy, moaning as they penetrate her. Alex takes over from there, sinking them in the rest of the way, pressing her down a bit so her ass sticks further into the air. He lets out a soft moan. "Yeah. Might just rival Olivia's..." He murmurs. He crooks a finger at Olivia behind Rina's back, inviting her to join them as he languidly thrusts into Rina.
[Stupid fucking internet! I had to type this out TWICE.]