Harry's first magic outburst happens very early in his life(before age 5) and teleports him to the soul eater world, where he is adopted by the evans family where he becomes the brother to Soul Eater. Once soul goes to the death weapon and meinster academy, harry goes too and they both become partners with maka(harry will also be a scythe (maybe crescent rose from rwby) and maka will alternate between the brothers, while one is a full scythe in maka's hands, the other will fight with partial transformations(just like the chainsaw guy and the guillotine guy). Harry will also be a meinster, so he can wield his brother if the situation calls for it and he can use the "soul menace" tecnique black star and professor stein use)
.
Story starts after all of soul eater canon, with Soul Eater beeing declared the likely last death scythe(as with the peace with the witches, there wouldn't be more witch souls to colect) and all of that. Maka senses a small disturbance in harry's soul(the hogwarts letter trying to locate him(yes, harry would just become 11 there)) and uppon further inspection, the soul fragment of voldemort. After consulting death the kid, harry consumes the fragment and starts to transform into a death scythe, but he needs to finish the entire soul for it and can't consume any other souls before that, to find the rest of the soul, they get the help of the witches, and so the 3(harry, Soul Eater and maka) travel to harry's original world using a portkey made by the witches
.
.
.
.
.
I SO want to see dumbledore's face when the owl that should send harry's letter just gets lost and starts flying in small circles in front of him. When he inspects the letter, it will put harry's adress at the dorms of the death weapon and meinster academy in death city