What was the motive during the first trial?

Who was the first murder victim on Jabberwock Island?

She was behind wallpaper wrapped around a pillar

Hiyoko's body was not hidden at the crime scene

To be fair, his more accurate name is "Mechamaru" at this point... considering that he's a robot.

More accurately, the Four Dark Devas of Destruction.

Since everyone threw the fire grenades, it's unknown who threw the tampered one that ultimately killed Nagito.

No one was executed because the case is unsolvable

She was most likely to have thrown the grenade

She admitted she threw the tampered grenade

The group needed to kill someone to proceed

They are survivors of Hope's Peak Academy AND Remnants of Despair.

The former Killing Game participants being present

The traitor still being present in the group