(Solar: 22, Nayoung/Sowon: 18)

It is the rare occasion that the three sisters have to share a room because they are back in their hometown at their grandmother's place for a visit during the twins' summer vacation, and none of them seem to be able to fall asleep but are instead wide awake in the dead of the night.

"Unnie," Sojung mumbles.

"Hmm?" both Yongsun and Nayoung answers.

"I was calling Yongsun unnie," Sojung rolls her eyes as she says.

"Pffft," Nayoung shifts within the sheets, creating more noise.

"Yes, Sojung ah?" Yongsun decides to ignore the older twin.

"Why do I have to address Kim Nayoung with honorific when she's only two minutes older than me?" Sojung plainly asks.

Yongsun stifles a laughter, while Nayoung turns back with narrowed eyes and furrowed eyebrows.

"What?" Nayoung raises her voice.

"Shut up, don't wake everyone up," Yongsun hisses at Nayoung.

"Tsk, let's sleep," Nayoung clicks her tongue and turns away again.

"Um so my question?" Sojung doesn't give up.

"That's because we're being traditional and even though it's only two minutes she's still your older sister," Yongsun somewhat patiently explains even though she thinks Sojung understands.

Sojung is about to protest but stops herself. "I know that," she mutters with annoyance in her voice before turning away in the sheets to face the wall.

"What I don't understand is why our names are so differe