The bird alchemist (FMB harem x Trap Nero reader)

(A/N: I got this idea after watching the movie)

During WW2 some Germany acult scientists were experimenting on was to open a gate, it was said that they need a thousand souls for the gate to appear and they have enough souls but one day when they finally opened it everything went wrong, black ribbon like hands dragged and disintegrated many people and for one prisoner it was there chance to escape. They ran to the gate and once he step foot inside the gate closed, when he woke up he change into a homunculus chimaera bird and is in a world similar to his but different, for instance alchemy evolved like science, what will happen when this bird meets a short state Alchemist and his brother.