I'm amazed at Rentaro's will to not go wild on all these lovely ladies. All that restraint is gonna come to a head one day, and who knows what will happen?
Even as an American, I get it. Ever since high school, I've almost always been addressed by my last name, or some form of it. Hearing my first name from someone other than really close friends or family just feels off to me, almost like you have to earn the privilege of addressing me that way.