I say unusual in the sense of Japan seems to be the only one to have solved the issue of how do you transport 2 kids on a bike not with "big box" like the dutch and subsequently the entire western world but via 2 seats, they're apparently very popular over there as a means of transportation.
I'm really sorry that happened to you. I'm not the person who was arguing that helmets weren't necessary. I wrote the nerd emoji comment because I thought it was absurd that the debate was even happening and honestly believed that the anti-helmet person was just pulling the other person's leg, now I see that that wasn't the case at all.