"To Love Ru" centers around Rito Yuuki, a high school student whose life takes an unexpected turn when Lala Satalin Deviluke, an alien princess from the planet Deviluke, crash-lands in his bathtub. Lala, fleeing an arranged marriage, decides to stay on Earth and declares Rito her fiancé, despite his initial reluctance. This sets off a series of comedic and romantic misadventures as Rito navigates his new reality, balancing his ordinary life with the chaos brought by Lala and her extraterrestrial companions.

The narrative expands as more characters are introduced, including Lala’s younger sisters, Nana and Momo, who arrive on Earth to bring her back but eventually decide to stay. Other alien beings, such as the shapeshifting Peke and the stoic assassin Golden Darkness (Yami), further complicate Rito’s life. The story also explores the dynamics between Rito and his childhood friend, Haruna Sairenji, who harbors feelings for him but struggles to express them amidst the growing number of romantic rivals.

Themes of love, friendship, and self-discovery are woven throughout the series, often framed within humorous and lighthearted scenarios. The plot frequently shifts between slice-of-life moments and more fantastical elements, such as intergalactic conflicts and advanced alien technology. As the story progresses, Rito’s relationships with the various female characters deepen, leading to moments of emotional growth and romantic tension.

The series is structured into multiple arcs, each introducing new challenges and characters while maintaining a focus on Rito’s evolving relationships. The tone remains predominantly comedic, with occasional dramatic undertones, particularly in later arcs where the stakes of interplanetary politics and personal conflicts are heightened. The interplay between the human and alien worlds serves as a backdrop for the central romantic comedy, creating a balance between the mundane and the extraordinary.