Just mouth for now.

"Um... Just use your mouth and hands this time," he said after a moment of consideration. Again, he wanted to take things slow, and figured a tit fuck could be the next step.

"As you wish, my Master," Momo grinned, lightly fondling his testicles with one hand, and stroking his length with the other. She lowered her face towards the tip of his manhood, and extended her tongue out from between her lips to begin licking at it.

"Oh..." Izuku moaned, clenching the sheets as he processed the sensations. It felt amazing. He had masturbated before, but it didn't compare to this. He looked down at Momo while she swirled her tongue around the sensitive skin of his tip.

Momo was fully absorbed in her task as she worked to get her Master off, enjoying every moment of it. There was no hesitation or shame in her actions. One of the best things about being a genie in her mind was a total liberation from all inhibitions. All people had their sexual desires, and society, due to things like religious influences looked down on those who were too in touch with said desires. Like many others, Momo had internalized those judgements, thinking things like it was bad to be a slut. But she fully understood now, that while some restrictions, such as rules protecting the underage, made sense, any act that happened between consenting adults was no one else's business. No one else's place to judge. Neither a slut, nor a prude was in any way superior to the other. They had their own definitions of self respect, and both were equally valid.

Momo, for her part, was taking pride and fulfillment in her ability to please her Master sexually. She lowered her head further, opening her mouth to engulf his length, taking his shaft into her inviting mouth, letting it hit the back of her throat, but triggering no gag reflex. Another benefit to her new genie nature.

"Ah!" Izuku gasped, his grip on the sheets tightening as she began to slowly bob her head up and down on his manhood. "Oh... Yeah, keep it up..." he managed to get out though gritted teeth.

Momo did not need telling twice, and continued to caress his balls as she sucked vigorously but slowly. She knew he was still new to this, so would have trouble lasting long, so she used her supernaturally granted skills to get him going slowly. She wanted him to be able to savor this moment.

Izuku groaned as he felt her tongue run along the underside of his cock as she continued to serve him orally. He reached a hand forward, placing it on her head. Not to **** her to go faster like he had seen in occasional porn, but a tender caress of her hair instead. In response, she looked up at him with doe eyes. She then began to speed up slightly of her own voilition after several minutes of this, aiming to bring him to the edge. Once there, she slowed again, but not too much. Just enough to keep him right there, on the edge of orgasm as she savored the salty taste of the precum that had leaked out the tip of his cock. She kept this up for about two minutes.

"...I can't take it anymore Momo," Izuku panted, his eyes tightly shut. "Please, make me cum!" At those words, Momo immediately began to attack his length with her mouth, sucking and gulping voraciously. Izuku lasted all of fifteen seconds of this, before he hit his limit. "Ah!" he gasped out as his seed exploded out from his shaft, filling Momo's mouth. She gave a muffled moan of delight of her own, taking it all into her mouth. She waited until the spasms of his shaft and spurts of seed finally finished, and then pulled off, closing her lips as his tip emerged from between them with an audible pop.

Izuku panted, and gazed down at Momo, who met his gaze, before slowly opening her mouth, extending her tongue, showing him all the seed she had collected, before retreating it, closing her mouth again, visibly swallowing, before repeating her former action, showing it was all gone. She had an air of bliss about her that matched his own satisfaction. If there was any moment that convinced Izuku that Momo was genuinely happy with her state as his servant, this was it.

(You guys may have noticed this chapter was longer than the norm from me. That's by design. I try to put a lot of work into writing engaging sex scenes, but storywise, I like the idea of leaving plenty of divergence points. Keeping story chapters to one major development at a time gives anyone who might want to branch off more options to work with without having to either reiterate the first part of a chapter, or disregard the last part of it.)