* Dorgencalibur: Belonging to Jaster, the Dorgencalibur is permanently equipped to him from the moment you obtain it in the story. You can't remove it or equip it to other characters.
* Sword of Sin: Similarly, the Sword of Sin is permanently equipped to Kisala from the moment you acquire it. You can't swap it out or give it to another character.
These weapons are unique and essential to the characters' gameplay, so they are not meant to be interchangeable.
However, you can enhance them! Both the Dorgencalibur and Sword of Sin can be upgraded through the "Evolution" system. You'll need to find specific materials and have the necessary funds to upgrade them, boosting their stats and making them even more powerful.
Keep in mind that these two weapons are already incredibly strong, so upgrading them may not be strictly necessary but can definitely help you in the later parts of the game.