It's not an arc (yeah because arc means more than one episode), it's an episode about Risa
There will be another episode about Miya with the Blu-Ray.
Other than that, it was a great episode. Junichi was a real man in this episode. I'm proud of you Junichi ! Umehara too. He is a really good friend ! And of course, Ayatsuji was really great. The kick scene was fabulous
And the end with the opening and the epilogue was really great too
The only thing that I don't like is, Ayatsuji, why why did you cut your hair
? Whyyyyyy
? ....
Oh yeah maybe there was also not enough focus on Ayatsuji problem.
But overall, I have really enjoyed this episode and this arc. Best Amagami's arc !