Is watching anime that contains magic and supernatural powers, and wishing for the victory of favorite characters who use these powers, considered an affirmation and acceptance of polytheistic evil, and thus does one become an infidel?

You must stop watching these films, and strive against your soul to rid yourself of attachment to them, and occupy your time with what benefits you in this world and the Hereafter. The viewer of these films does not become a disbeliever merely by interacting with them if he denies the disbelief within them.