Nisekoi centers on Raku Ichijou, a first-year student at Bonyari High School who looks like an ordinary teenager but is also the sole heir to a formidable yakuza family. Ten years earlier, he made a promise to a childhood friend and was left with only a pendant with a lock, while the girl took the key that can open it when they parted. Years later, Raku wants nothing more than an ordinary school life far away from his yakuza background, especially if it means staying close to his middle school crush, Kosaki Onodera. That hope falls apart when the American Bee Hive Gang invades his family's turf and Raku is forced into a humiliating arrangement: he must pretend to be in a romantic relationship with Chitoge Kirisaki, the beautiful daughter of the Bee Hive's chief, to ease the tension between the two groups. The lie starts badly. Raku and Chitoge fall in hate at first sight, with Chitoge seeing him as a pathetic pushover and Raku thinking of her as little more than a savage gorilla.
From there, Nisekoi builds its romantic comedy around that false relationship, the city's uneasy peace, and the mystery of the promise Raku has carried for years. As more girls enter his life, each connected somehow to his past, the situation grows even more tangled with figures such as Marika Tachibana and Seishirou Tsugumi complicating both his search and his feelings. What begins as a forced alliance between rival families turns into a broader story of misunderstandings, old memories, and competing affections, as Raku keeps looking for the girl linked to the pendant, the key, and the promise that still shapes his heart.