Kimi ga Shinu Natsu ni - Vol. 7 Ch. 30 - In The Summer When You Die

[MangaDex]

 

[redscizor]

Again a cannonic event, he cant kill Fukku and now returned at his time line

 

[AnimuVsMango]

Literal Deus ex Machina

 

[Bearman851]

So, this is timeline C.

Timeline A is where Ghost Tanigawa is from aka the timeline where she originally died.

Timeline B is where Yamano is from, where he met G. Tanigawa, and where Sasakura was attacked (and most likely died).

Timeline C is where G. Tanigawa and Yamano NEVER met. Meaning any social developments from Timeline B (aside from between Yamano and G. Tanigawa) have been negated.

To continue off of where I was before...

Welcome to Timeline D.
Timeline D is an exact copy of Timeline B, but Sasakura was NOT attacked. All social developments from Timeline C are disregarded, aside from G. Tanigawa and Yamano.