Heroslayer said: Wouldn't Touma's hand just nullify the Red String of Fate?
According to the entry on Imagine Breaker in to To Aru Majutsu no Index Wiki, Index once theorized that Touma is so popular with girls because he negates their red string of fate! In other words, he negates them eventually falling for whomever their destined one was and so they end up falling for him when he acts like a big damn hero in front of them! The guys who complain about him taking all the girls for himself may very well have a point!