Raku Ichijou is the sole heir to a yakuza family. Ten years ago, Raku made a promise to his childhood friend. Now, all he has to go on is a pendant with a lock, which can only be unlocked with the key which the girl took with her when they parted. Now, years later, Raku has grown into a teenager, and all he wants is to remain uninvolved in his yakuza background. However, when an American gang invades his family's turf, Raku is to pretend that he is in a relationship with the daughter of the gang's chief, so as to reduce the friction between the two groups. Unfortunately, the girl is convinced he is a pathetic pushover, and in Raku's eyes, she is like a savage gorilla. Nisekoi follows the daily antics of this mismatched couple who have been forced to get along. With many more girls popping up his life, all involved with Raku's past somehow, his search for the girl who holds his heart and his promise leads him in more unexpected directions than he expects.