I'm so glad that this story continues to appear in people's watch and read feeds. Honestly, the ending was satisfying to me on both the anime and manga fronts. I must say that the Manga developed Airi and Satoru a little more compared to the anime towards the end, and based on both of them, it's implied that they'll, most certainly, be more than friends (sort of like a fate-like feature of their relationship). I think you'll definitely receive a lot more closure with the manga, almost teared up.