Nisekoi: False Love (Blu-ray release 2019-6-5) is a live action adaptation of a manga, about the protagonist pretending to be in love with the daughter of a rival gangster family in order to prevent wars. Viewed as a standalone movie, it is a safe romantic comedy that has a complete story and is enjoyable with manga style exaggerations.
The manga has 229 chapters, so the movie has to drop many things and most of the subplots from the source material. Most importantly, the defining element of harem in the manga is mostly vanished from the movie. The secondary love interest in the movie has much less screen time, and the tertiary one gets so little to the point that she can be eliminated without affecting the story. The complexity of multiple fake key holders in the manga is also reduced to only one real key holder in the movie. The manga keeps what happened in childhood as a key mystery that is not revealed until the end. In the movie, the simplified truth is revealed very early. There is not any doubt in the movie about who the protagonist’s final choice will be, but in the manga it is much less clear before the end.
So, the harem is gone. There is no mystery. The ending is predictable. I will not say the movie is bad, but a single movie is not sufficient to present what makes the manga great. Considering the length and complexity of the source material, I think the movie is actually a reasonable adaptation.