in the shell

One thing I still don't understand from the first GIG is how Serano was killed in first GIG, and what the perp's motives were. Was he hired by Yakushima or another conspirator?

Were yakushima and the other conspirators finall convicted at the end? I know the old ruling party was defeated in the elections as a result of the scandal, but I thought it was unclear what happened to Yakushima in the end, especially with Serano never making it to the witness stand. I wonder why section 9 still needed to tie up loose ends with regards to Yakushima's fellow conspirators in season 2, with Cash Eye.

I think it is a mystery of how Serano died, all I know is that Serano lifted the door handle of the car up and next there was a look of shock on his face, I doubt the car was rigged to explode, since we would have seen the explosion as the mysterious guy is walking away from the car so I would say that the car was rigged to fuse Serano's cyberbrain. Yakushima could have been involved in the death of Serano since Ernest Serano was going to testify in Yakushima's trial and Yakushima's prosecutor in Yakushima's previous trial was ran over by a train, Yakushima had a role in his death.

From an issue of Anime Insider, it mentioned that Section 9 at the end of episode 26 was sent to investigate Serano's death.

I think it was a car-bomb.

Weirdly, what bugs me is its a really strange denoument to the series. After all the effort they went to destroy Yakushima, the poor guy of Serenno still ends up executed.

There's a LOT of corruption in the SAC world.