Couldn't the soldier or child walked onto the bridge at the same time as those on the other side, then 4 people would of technically been on the bridge at the same time to walk towards the station?
@Random Reader yes but, that "even number" thingy for the bridge was only applied later when that girl's constellation sponsored her. so either way, they would have never known that an even number had to cross until both the soldier and child were at oksu station. [poco:0]