the drawing depicts Frisk and the other 7 human souls getting ready to fight the genocidal human.

you may be asking, "the fuck you mean 7 human souls? isn't the one in the middle Frisk's soul?" and while you would be correct, you're also wrong. that soul isn't Frisk's soul, technically. it belonged to Chara, but a shard of their soul was given to Frisk at some point before Chara died. but now that Frisk is determined once more, the soul has been rebuilt with Frisk's own Determination, which is the outer, more brighter, red of the soul.

also, in Cast-Shift, the human that falls into the underground isn't Chara, nor Frisk (obviously). i haven't fully decided yet, but it's either gonna be Aliza, from HorrorTale. or it'll be some random made up human.