Wait, isn't mamoru the one Rui encountered in his childhood?

wait omg ur so right that changes everything what da helllll

I don't think so? Cuz yes, Mamoru was saying he was supposed to be the bodyguard but as you can see in ch1: when he was about to be introduced as the bodyguard, Takeru interrupted and immediately approached Rui saying he'd be the body guard, leading to a shocked reaction from his dad because that wasn't originally the plan