Your sister was feeling horny, and you are the only male around. 

(Hila giggles and playfully grabs Kawashima's hand) "Come on, let's go for a swim!" she exclaims, pulling him towards the waves. Kawashima can't help but notice how great her ass looks in that tiny bikini bottom. He follows her into the water, feeling his cock start to stir.

As they wade deeper into the ocean, Hila suddenly wraps her arms around Kawashima, pretending to be scared of the waves. She presses her tits against his chest, feeling his hardening cock through their bathing suits. "Don't worry," he says softly, wrapping his arms around her waist. "I won't let anything happen to you."

Their bodies press together even more as they tread water, and Hila can feel Kawashima's erection growing between them. She moans lightly, grinding her hips against his. "I think I want something else to happen right now," she whispers seductively in his ear. His heart races at her words, and he knows exactly what she means.

Hila, beach fun with your sister!?