So this feels like a completely different story to part 1 with the same characters but anyway. This clearly retcons the end of part 1 when MC shows up to school with their uniform worn properly and hair dyed black and the girl in their body showing up like a delinquent. This was clearly a setup part for a 3rd part in which the MC will probably have to have sex with the girl that's in their body to get the proper magical power but will be probably end with the MC getting fully corrupted.
@JustReadingShit could be that after their look changing shenanigans at the end of the 1st chapter they could have had a talk and agreed to actually act like each other
also yeah i kinda agree that there's a third part to this that will end up in the MC getting corrupted or at least will actually be permanently stuck as the girl (as is the case with majority of his previous works)