If you want to enjoy the same wholesome slice-of-life fun as the anime then just read vol. 1-4 (chp. 24) and extras 1-3 in vol 10.
If you want to enjoy the continuation and have a really good slice of life, you can read through to vol. 7 (chp. 42) and extras 4&5 in vol. 10.
The waters get murky in vol. 8 and then vol. 9 is - well, infamous - at this point, but having not known exactly how the ending would go down and it ultimately being not as bad as I had dreaded, it was still uncomfortable but ultimately didn't ruin the story for me. Now, though, I am still stuggling for a physical copying of vol. 9, which seems to be impossible to get in english from anywhere - it's become my white whale.
I can, however, honestly say that this manga is incredibly good. It is heartwarming and hard to fault as a slice of life. While I don't advocate spoiling stories, I think going on this journey with an idea of the destination is probably the best way to go about it.
