Kinda anti-climatic, really. The mom just got told off, nothing happened to yuri and her development, and, while it is sweet that they ended up working together for awhile until he would graduate and that he finally saved up to get there, there's just a lot of unanswered questions this ending brings that I don't like.
Where were the grandparents this whole time? Why did no one consider it as an option?
What happened to Yuri now that her first and only love left town? Did she ever find out about Souta's mother? What would be here reaction to the news?
Why was the mom dismissed in a throwaway line? Why Rehab, which implies drug addiction, and not some kind of therapy or mental institution?
It wouldn't have been my first pick for how to end the story, if I'm being honest. It clashes a bit to much with the earlier tone and themes.