Who killed him?

                                    

                                          
«Kyoko Kirigiri's perspective»
The elevator grinds to a halt, shuddering into place. Everyone is silent: the tension is unbreakable. I look around my classmates- one of them is a murderer. 
As we walk to the stands, I survey everyone in more detail. Sayaka looks petrified, her navy hair catching the light of the room, Makoto right beside her. Neither of them would be strong enough. Aoi stands close to Sakura- they both are suspects. Aoi's strange reaction to Leon's death further puts her under suspicion. Apart from them, Mondo, Hagakure, maybe Byakuya or Celeste and Kiyotaka all look strong enough. It could be anyone.
"Ok, let's start of with what we know. Leon was killed in his own room at 1:00 am." Announces Makoto. 
"Wait." Everyone looks at me. "His shower room locked-"
"He was a girl this whole time?" Queries Junko, wrapping a lock of hair round her finger."Omg, that's crazy!"
"No. His room was switched with someone. He was killed in someone else's rooms."
"But who's? It could be anyone?" Yells Mondo, slamming his fist on the table. 
"It seems it would be the murderers." Byakuya snaps. "They killed Leon in their own room, by luring him in somehow. Then switched the name tags." 
"Who would do that?" Whimpers Chihiro. 
"There's one more piece of evidence!" Celeste smiles. "I found this note in Leon's room. It's an invitation- to Aoi Asihina's room. She is the killer."
Aoi looks petrified,then a determined look flashes into her face.
"You're right. I killed Leon!" She screams, tears pouring down her face. 
"Wait!" Makoto yells. "When we searched the room, we didn't see the note. It must have been added after the murder! To frame Aoi." 
"No! I killed him!" Cries Aoi, hysterically sobbing. "Why won't you believe me!" 
"Aoi." A calm voice cuts through the hysteria. "I can't let you take the blame." Sakura walks to stand beside Aoi. "I killed Leon."