(continued)
Beomgyu: Actually... Taehyun, what's your problem?
The others looked back at Beomgyu, before looking at Taehyun. Taehyun rushed over to Beomgyu and knelt down.
Taehyun: G-Gyu? What do you mean? Are you okay? Don't get up you need to rest-
Beomgyu narrowed his eyes and pushed Taehyun's hand away.
Beomgyu: Stop acting all caring for me. You're only my friend right? It's not like we're dating-
The others widened their eyes as Taehyun's hand dropped to the ground, his mouth open.
Taehyun: Gyu! What do you-
Beomgyu: Oh shut up! Yeonjun already told me everything so don't make excuses! I know how you used me!
Yeonjun bit his lip and looked down as Taehyun scoffed.
Taehyun: Right. I get it.

Taehyun stood up, his eyes cold. He walked to Yeonjun and punched him on the face.
Kai and Soobin widened their eyes and ran upto them, holding Taehyun back. Beomgyu put his hands over his mouth, silently watching.
Yeonjun staggered back slightly, holding his lips which were dripping blood.
Taehyun: You jerk! How could you-
Taehyun looked at him in disbelief and dragged Yeonjun out the room.

Kai: T-Taehyun come ba-
Soobin: Kai...let's leave them, they need to talk.
Soobin sighed and walked over to Beomgyu, who was shocked.
Soobin: Beomgyu, we need you to tell us what Yeonjun said to you... What happened?
Beomgyu: I- He just told me about who he was to me  and how you guys were like... Because my memory....
Kai sighed.
Kai: When was this?
Beomgyu: After I woke up, you guys came and then went out some time later to let me rest. Then Yeonjun came in.
Soobin sighed again and leaned back in his chair.
Soobin: Beomgyu...what did Yeonjun say about Taehyun?
Beomgyu: That Taehyun was my ex, and he used to hurt me, and that we broke up because Taehyun cheated. Yeonjun said we started dating a while later...
Kai widened his eyes.
Kai: That's completely fake! Taehyun loves you and never has hurt you! You guys were such a sweet couple! You never broke up in the first place!

Beomgyu sighed and leaned back in the hospital bed.
Beomgyu: I'm sorry. But I can't trust you. We barely know each other now, and Yeonjun already told me you guys would react like this. Honestly...

I believe Yeonjun.