are we talking about wataei's favourite kinks or what kinks i like to project them onto.. either way i think their first time would be really soft and vanilla but they slowly discover some kinks
i think eichi specifically would be into breeding kink. not because he actually likes it but it's just so he could carry wataru's child to make sure he doesn't leave him. hell i think he has attempted to poke holes on some condoms before but wataru always notices somehow and secretly replaces those with working condoms.