well, it's bad plot, but it's kept me entertained...
the retcon sword should have some limitations.. he needs to 'write' stories that match up between people, think about the party that's going down at Ichigo's house, what if they start recalling memories from their BFF shimatsuki and figure out it doesn't add up? the spell breaks.

still, Ichigo could ask Orihime to reject the effects of the fullbring from both him and the other guy, maybe make up a story that it's making them both crazy.