In chapter 2 The Boys, was already told how Kyuhyun and Yoona met. It’s also mentioned again in chapter 25

Yoona's POV

I see Siwon sunbae is walking out from teacher office room when I’m out from Seohyun’s class. Seohyun’s class is near the teacher office room.

I wait for him to walk in front of me then I can walk slowly behind him while adoring his perfect backside figure. I smile crazily. His uniform coat is really fit in his body. His black hair is shining. Even from behind he looks so handsome. I take my cell phone in my pocket to capture him.

I’m about to ready to take  picture of Siwon sunbae’s back, but one thing that I never expect before, he turns himself away all of sudden and I’m not ready at all. Oh My God, what should I do? Does he know that I’m stalking him right now? Without second thinking, I turn left and run as fast I can. I die, I really really die. I don’t know where to escape then I see a door and open it. I close the door fast and face the door while panting heavily.

I sigh and press my chest. Seriously how can I act stupid earlier?

“What are you doing here?”

I hear a voice behind me that makes me startle. A male’s voice. I turn around and the first thing I see is someone whom I’ve never seen before. He looks at me distinctly. I wander around then my eyes become wider and my mouth is also opened widely when I realize what room that I am in right now. Male student rest room. I can feel my face becomes red. Im Yoona, you are really the stupidest girl ever. This is totally the worst day of my existence in this world.

“Are you a ert?”

He asks me again with a smirk on his face. I can feel this guy in front of me is making a joke of me. How dare him.

“I AM NOT!” I don’t realize that I just yelled at him. Somehow, I get into male rest room without any purpose, but the way he asks me I’m a ert or not really hurt my pride. He’s too much. I know it’s my mistake but he supposed not to say something like that. “I’m sorry. I…I don’t realize if it’s a male rest room.” I hit my head gently. My voice becomes weak and I don’t want to face this guy’s face.

“Then why are you still here? Lucky you, I’m the only one here right now. What a weird girl!!” He walks away then opens the door. “You still don’t want to go out, Weirdo?”

I clench my fist and bite my bottom lip. I turn around and runaway to escape from that male rest room and from that evil guy.