All Souls Night is an excellent introductory scenario for Ryuutama, with a great emotional core and well thought out, flavorful encounters. I frequently reccommend it to those new to the game looking for pre-written content.
As written I think the scenario really shines when run in 2-3 sessions. Although Pureka includes several optional encounter tables, I think the game is much better if you use them, and captures more of the feel of journeys in Ryuutama.
If you're committed to running this in a single session, I recommend cutting the Witches Tasks and going straight to the "Preparing for the Ritual" section, which should cut the game down to one-shot length.