Gave it a test and if Munkidori is on the battlefield when Future Sight activates, it will retain the boost and (likely) have a chance to procc Toxic Chain. The only requirement for both is that Munkidori needs to be on the battlefield when the move deals damage.I wanna make sure, if it leaves the field, then returns the next turn, will Future Sight retain the boost? The way you worded it, I'd assume no.