what adam sandler movie, because that is not the premise of big daddy... the premise of big daddy is screw my best friend I am going to kidnap his kid he doesn't know he has by pretending to be him and use the kid as a tool to get back with my ex which is nothing like usagi drop's premise.
So I needed to look it up because god knows I haven't seen this movie in over ten years, but:
Rather than give Julian to a group home, he decides to hang out with the 5-year-old boy until a new family is ready for him. In caring for him, Sonny discovers a new purpose in his life and a deep connection with Julian as a father figure. But Social Services rep Arthur Brooks (Josh Mostel) discovers that Sonny is posing as Kevin, and insists that he give up Julian. Brooks takes Julian and decides to press charges against Sonny.
But that's the sentimental part I remember.
Well, also the court scene with this:
The judge grants custody to Kevin to the dismay of Julian, who wants Sonny as his father. Sonny tells Julian that it can't happen because his real father is present, but they can be friends.
--
There's a difference between sentimental and SENTIMENTAL.
I just don't see how Aria is the all-caps one, which I assume you are using as a pejorative, while Usagi Drop is a "positive" form of sentimentality.
Of course Usagi Drop is sentimental. But it does it without pretending like the world owes you a favour or that if you wish for things really hard or are a good person then your wife comes back from the dead.
If you want to raise a child you have to make sacrifices, you can't get that career advancement you wanted, you can't stay out late drinking, you can't date as easily, these are all factors that the show deals with unceremoniously.
Well, my point would be that because this is a work of fiction - and even if you leave off the second half - unless the author is trying to make a comment and play with audience expectations, you know exactly what will happen to these characters. It's not a show about tension because it's inevitable that the dude will learn to be a father and the girl will learn to accept him. Because, hell, that's what people watch these stories for.
Even that show that came after it, PapaKiki, works in the exact same manner. It just throws in sprinkles of anime vomit all over it to make it more palatable for an otaku audience.