A story of a less-competent individual who isn't fit for job and work cycle that he's been thrust into by his older brother. Now finding himself in a the immature schemes of a naively obsessed highschool girl that sort of accidentally helps him stop blaming himself.
It's short and sweet. It accomplishes in 19 chapters everything that 100+ chapters or more would of other manga. Just without the mountainous amounts of filler material or uncalled for drama. Does give off fetishy vibes though because of the obvious Master/Servant thing it dances around.
Ending is actually good for what it is. Anything else I feel would have been a little off-base and unfulfilling for this story.
Being short though it does leave less impact in you than something that takes the affordmentioned 100+ chapters to do the same thing. But I chalk that up to subconscious sunken cost. Do I want to remember Nisekoi 8 years after it ended? Not especially? Will I remember this in 8 years? Unlikely. But I'd still read it again if I'm reminded about it.