Leiko is a character in Vayneline. He is a Light Blader who is on the same prison desert planet as Leiger.
He is part of the Sandflit tribe, a group of fighters that have tremendous speed and reflexes. It is later revealed he came to this planet to track down and kill a man named Izulu who had committed a dishonor against his tribe.
Leiger and Leiko share a special connection together after the events in VayneLine Fate Reset, it is never clear if this mental connection is real but heavily implied to be real.