The Princess Diaries, Volume VIII: Princess on the Brink

The book opens on the first day of school and Mia Thermopolis is now a high school junior. Her best friend, Lilly Moscovitz, is dating J.P (formerly The Guy Who Hates It When They Put Corn In His Chili) and Tina Hakim-Baba, who is still with Boris, is convinced that Lilly and J.P. had sex over the summer break because they spent a weekend together in upstate New York. Mia does not agree, reasoning that Lilly would certainly have told her, because Lilly tells her everything, but begins to doubt this when Tina shares that Lilly touched Boris's penis when they were a couple, something Lilly never told Mia. Mia has also decided she no longer wants to be Student Body President, but is struggling to find a way to tell Lilly who is set to nominate her for the position again. Unfortunately, Mia ends up being the only nominee for president.

Mia's Grandmere has decided to purchase a condominium in Manhattan and, while waiting for it to be remodeled, has moved out of the Plaza Hotel and into the W, which she hates, due to its modern decor and later into the Ritz-Carlton, which she also finds unacceptable.

That same night, at a dinner at Number One Noodle Son, Michael tells Mia that he needs to spend a year (or more) in Japan because a robotics project on which he has been working (a robotic arm) has caught the interest of a company that wants to develop it for use in the medical field. Mia is extremely upset about this, especially after Michael tells her it will be easier for him to be away from her since she still does not want to have sex with him. Grandmere gives Mia the key to her vacated suite at the Ritz, which plants the idea in Mia's head that if she sleeps with Michael, he will not want to leave. On the night that Mia plans to have sex with Michael, she finds out that he had sex with Judith Gershner and had never mentioned it (he mentioned the friendship, but not the sex) and is no longer a virgin. This leads Mia to break up with him.

On the day Michael is supposed to leave for Japan, he goes to Albert Einstein High and sees Mia accidentally kissing J.P. (she meant to kiss his cheek but he moved his head and she kissed his lips). J.P. has just broken up with Lilly, and Kenny tells Lilly about the kiss. Now, her former best friend and former boyfriend are no longer speaking to her. When Mia goes to explain what happened to Michael, his plane to Japan has already taken off. J.P. asks if Mia would like to see Beauty and the Beast with him, and she says yes. But before she goes, she e-mails Michael and writes, "Michael, I'm sorry," the only thing she can think to say.