What is the ruling on naming a person after a character from a disbelieving anime, or discussing a disbelieving anime, or watching discussions about a disbelieving anime?

You must stay away from everything related to anime that contains scenes of disbelief (kufr), and this includes what was mentioned in the question, as it involves a kind of endorsement and satisfaction with those games and promotes them. However, what was mentioned is not considered disbelief (kufr) or apostasy from Islam.