God not gonna lie I loved this mini arc a lot. It did absolute wonders for character development for Komi Shouko and her family, and introduced a character that (to me) hits so close to home. Rei is a very colourful character and fits well with the rest of the cast: she's playful, caring, mature yet childish, and more. While it was a bit weird not to see the gang all the time, this arc was really about Komi doing her best on her own to try to make a new friend, taking inspiration from the gang. It just goes to show how much Komi has progressed since the beginning.
Also, Rei is now canonically friends with Susie Deltarune.