Body Swap Manga features the very popular story telling device called the body swap. Such a troupe generally comes in strongly scientific fictions or supernatural fictions.
The story follows a basic path, with varying concepts and causes of course. There are two beings, they may be human, animals or supernatural beings even Gods, who exchange their minds and find themselves in the body of the other. The two characters get the opportunity to see the world through their swap partners eyes, however, in the new body they still retain their mind and spirit and hence, bring a new spin to the new character.
Believe it or not but this body swaping genre of manga includes some great manga like:
If the swapping happens without technology, then a magical item can be involved in the swap. These can be amulets, heartfelt wishes as has been in several manga or it can even happen through quirks in the universe as well. Usually, as the manga comes to an end, the switches are typically reversed.
This usually happens when the subjects of the swap have figured out what they lacked, and have fresh preservative. Once their world views have been expanded they find the spell or the incident reversed.
Is it always Sci-fi manga?
Sci-Fi manga which are accompanied by technology, other those gadgets which have advanced to the point that they look like magic, are usually accompanied by a mad scientist or an organization of mad scientists. These body swapping devices are usually characterized by their extremely and dangerously experimental status, they usually have straps, helmets with complicated dangerous looking cables running across them.
These are mostly connected to central systems, the types of which vary with each story. These systems usually malfunction as well before their effects can be reversed. Those who do not have complicated machinery usually resort to brain transplants. The body swap trope is usually accompanied by horror. More references can be taken from this answer on quora.