Loli falls in love with classmate because he's the only man that can keep pace with her on topics of math, science, and physics. She finds out his dream is to go work with NASA, not just because he has the smarts to do it, but so he can move to America and marry a busty, blonde girl he can fuck like mad every day.
Loli panics until hatching a scheme to create a body change potion to make herself the girl of his dreams to seduce him. Lots of shit happens over the course of 150+ pages, including another potion that body changes guy into a woman and the Loli futa-fucks his womanself.
Story ends with her being comfortable with her body, guy marrying her even though she's a loli. He's even fine having sex with her real, loli, body. But they occassionally still pull out the gender/body morphing stuff just to spice things up in bed.