Is it permissible to imagine using magical techniques, such as the famous hand seals in the anime "Naruto" and "One Piece," knowing their invalidity and fictional nature, and without believing in them or imitating their users, just as one might imagine cutting a mountain?

It is not permissible to imitate the actions of sorcerers and the like, even if one does not believe in them, because merely imitating them and performing their characteristic actions constitutes an imitation of them. It is mentioned in "Kashshaf al-Qina'" that imitating wine drinkers is forbidden, even if the beverage itself is permissible, if the gathering includes an arrangement that resembles the sittings of wine drinkers, due to the imitation of people of corruption therein.