Have her give him a titfuck.

Luffy then wrote, "Marguerite will give Monkey D. Luffy a boob job, and despite not knowing why she is doing it, will enjoy it, as well as the taste of his semen."

Marguerite blinked before turning around and walking to him and kneeling before him. "Um, I'm not sure why I'm doing this, but... I feel I need to put this between my breasts," she said, proceeding to grab his dick and put her boobs around it.

"Oh, this? It's just something that women do to men," Luffy sniggered as she started working on getting him off. Her innocence when it came to sex was cute. She wouldn't know about it on an island of just women who had their own method of reproduction, whatever that was.

"Oh, okay," she smiled, finding this made her feel strange, but in a good way as she continued to rub her breasts over his length.

"Try licking the tip," he moaned, feeling good.

"Ah, okay," she blushed, leaning down and running her tongue over it as she squeezed her boobs together. She moaned at the taste, even more so at that of his precum.

He pumped his hips slightly as she kept going, and soon busted his nut, cumming all over her face.

https://thumb-p3.xhcdn.com/a/sjS0_sHNfBdvcvnUJ8uzkg/000/052/516/243_1000.jpg

"Ah! What is this?" she asked, not having expected it, but then she processed the taste of the seed that had reached her mouth, and she proceeded to start licking it up.