Headcanon where the Okumura Twins were born at the end of daylights savings day and Rin was born first but Yukio travels back in time and is born an hour before Rin.
Once they find this out, Yukio laughs and smugly rubs it in Rin’s face like “TECHNICALLY I’m the older one! Now you have to call me Nisan!”
Rin rolls his eyes and kicks him in the shin. “Yeah, uh huh, sure. Whatever, little bro.”
Rin is a lowkey salty but he knows he’s actually the older one because daylight’s saving is bullshit and he’s the one that escaped the vagina first, dammit. Let him have this.