I found this movie by accident. It is the live-action variation of a short manga by the same name.
We follow Kawachi Daikichi (Matsuyama Hanichi) right after his grandfather passes away. The entire family finds out that he has an illegitimate daughter but no one wants to take her on. Though Daikichi is young, he decides that he will take Kaga Rin (Ashida Mana) home and take care of her. We get to see him struggle to do the right thing for her while also figuring out the ins and out of fatherhood.
This is an excellent depiction of the sacrifices that you have to make for the well-being of your child. Matsuyama was excellent in his role and I would love to watch more of his work. I will say, though, this is no a movie to watch if your maternal/paternal clock is ticking. This has made me want kids even more now.