no it's not his brain, its more like his harem
or rather the way he influence others to join forces with him. Those are troublesome people that can get the trust of others easily. If Aleister leave touma behind then the consequence is probably touma would be already taken the world before he even destroy magic.
That's why touma is having vip attention on the dark side of the academy city as dangerous and do not touch sign on it with the signature of aleister crowley.