So episode 305 came out recently, therefore spoiler alert.
Most of it is concerning the past...
In the past episodes' flashback it was shown clearly that ..
- in this video,Takasugi lost his eye in a fight with alien.
- Shuoyou, teacher, is taken from his school and then his is returned to gintoki who cries helplessly.
- Shuoyou finds gintoki on battlefield and bring him to class with katsura and takasugi in it.
However in episode 304-305, this all contradicts
- Takasugi loses eye by attack of Oboro
- Katsura, Gintoki, and Takasugi are brought as prisoners and Gintoki is given choice to kill either students or teacher, on a top of mountain. Contradictory, to what been shown before many times: which is soldier hold gintoki down as teacher is taken prisioner and then on the same place his head returned and gintoki cries.
- In this version, gintoki is already part of the Shuoyou school and it's infact katsura and takasugi who join later on.