Piper Shapiro has the best mom in the world: Noura, a single parent by choice who always has a plan, whether it's for a spontaneous Saturday adventure or helping Piper navigate middle school as a nonbinary kid. They're a package deal, and they tell each other everything. At least, they used to. But then Noura invites Piper out to dinner with her girlfriend Gwinny . . . and Gwinny's son, Colton—a boy Piper knows, and doesn't exactly get along with. Piper panics when the realization hits: Noura and Gwinny are serious about each other. Suddenly, Piper's life as half of a duo has an expiration date, and ze is horrified.
To put a stop to any potential wedding bells, Piper makes a plan: break up the parents and keep things the way they are—the way they should be. When Gwinny surprises everyone with a get-to-know-each-other cruise for spring break, Piper's game is on—and Colton is in on it. The two of them work hard to make it clear that they are not one big happy family, even though it turns out that Colton might not be so bad after all. But when things with Project Break Up go a bit too far, Piper starts to question everything . . . and starts to realize that maybe a little change isn't a bad thing.