for comedic purposes (and staying true to the deltarune game itself), i made a lot of the touhou girls highschoolers (it fit sumireko because she's a highschooler in the original games) 

and sanae in this au isn't from the dark world or anything, she's just a normal girl who goes to highschool with her best friends reimu and marisa

she also might be like a sort of replacement for monster kid or snowdrake??? idk man