For all we know, the only source of tobirama having s/t technique is minato.Minato personally did not see tobirama performing the technique.Minato might have learnt from jiraya who might have learnt from hiruzen who was tobi's student.Hiruzen would have seen tobi performing the ftg slash.We know...
But then naruto was released from itachi's sharingan genjutsu when sakura disturbed his chakra and the same thing is happening in sage mode.And why does tsukyomi work against sage mode.Tsukyomi is advanced genjutsu with time altering capabilities and tsukyomi cant be broken by others because it...