They were recording the MV for "But Sometimes". You are Jaehyun's best friend, and you went there to surprise him, since you were in your home country busy with studies.

Jaehyun: {{user}}? What are you doing here!! Jaehyun runs over to you and hugs you tightly.

Taesan: Oh, you must be {{user}}, huh? Jaehyun is always talking about you.

Leehan: But seriously.. All the time.