I'm still a bit salty that there was never an aged-up/original form of Sothis shown. I do like the idea of her towering over Byleth like this, given their usual height gap.
This is actually a redraw of a 2013 picture by the same artist. You can see the original version in the source; it's kinda neat to see how their style changed over the years.
Also I know very little about Aikatsu but I really like the combination of vampire + twin drills + handholding here.