Request 34

A man (let's call him Alex) encounters a young girl (let's call her Amy) who ran away from home. Alex offers to help her, and Amy thanks him. Amy then swaps their bodies and runs away, leaving Alex stuck in the body of an elementary school girl, much to his horror and dismay. after the swap, Alex forgets his old name and face, and his education beyond elementary school, and realizes he thinks of himself as Amy now. However, he still retains his sense of self, so his personality isn't outright replaced or anything.