Nervously fucks her breasts!

"Mmm, you're clearly a tits man," Rias cooed.

"What can I say? Boobs are God's greatest creation!" Issei remarked. Rias laughed at that, fully agreeing, her mind all sexed up due to her transformation.

"Then perhaps you'd like to stick your manhood between them?" Rias suggested with a coo. Issei nodded, grinning eagerly, and Rias floated backwards and lowered herself to the floor. Issei straddled her waist, and started to insert his cock between her sacred valley, before pausing. "...Master?" she asked him.

He gulped slightly. He wasn't sure why, but this whole thing was making him afraid, though he couldn't fully grasp why. Like he was subconsciously scared of having sex all of a sudden. He shrugged it off, and slid his cock between her boobs, chalking it up to first time jitters. He put his hands back on them, squeezing them together, and fully slid his shaft into her cleavage. "Sorry, just nervous, I guess," he chuckled nervously.

"Ah, I get your virginity, so glad~!" Rias grinned, flipping her veil, and leaning down to lick his tip. He jolted slightly, and began thrusting back and forth. "I hope my assets give you the best time of your life, Master," she crooned between licks she timed perfectly to apply to his lower head to meet every thrust forward. "Your pleasure is my pleasure..."

"Unh..." he moaned, continuing to fuck her tits, squeezing them in his hands. "Oh God, this is way better than masturbation!" he grunted.

"Of course it is, Master, it's much more fulfilling to do it with another person than it is to do it yourself..." Rias cooed as he kept going, feeling the telltale throbbing of his manhood. "Your body knows when you are alone, and sex is meant to be shared..."

Issei simply grunted, before he erupted, his hot white semen coating her face and the top part of her tits. "...damn, it's over already?" he panted, going soft as he tried to catch his breath.

Rias smiled at him as she started licking at his release. "Don't be discouraged, Master, you just need practice to last longer..."

He was about to reply, when he heard footsteps coming up the stairs, and froze.