Sayaka’s dying message written in blood on the wall. When viewed upside down, the numbers spell "LEON".
Leon is unable to produce his personal toolkit, which was used to unscrew the bathroom door. Danganronpa: The Animation (Dub) Episode 3
As his guilt becomes undeniable, Leon breaks down in a violent rage, screaming denials before ultimately admitting he killed her in self-defense after Sayaka attacked him first. Sayaka’s dying message written in blood on the wall
Evidence reveals Sayaka initiated the room swap to lure a victim into her room, intending to frame Makoto for the murder to ensure her own escape. The Culprit Revealed Danganronpa: The Animation (Dub) Episode 3