Here we go:
Soundwave became a loyal Decepticon in Megatrons Decepticon army, he was always by Megatrons side as a right hand bot, Soundwave had a little help from cassettes such as Lazerbeak, Buzzsaw, Ravage, Rumble and Frenzy which made things easier in battle and also a lot more practical, why risk yourself in battle, when minions can do it for you.
Soundwave cared for his minions, giving them spare energon cubes, he weren't using.
Inside Kaori wanted to see Kōusei again, but she was just happy to be alive as Soundwave
Soundwave key operations during the war included, running a nightclub trap, hacking into Teletraan 1 and spying on both Autobots and Decepticons using trusty Lazerbeak and Ravage, while Rumble and Frenzy mostly tried to beat up Skywarp.
In the late 1990s, The Decepticons took Cybertron and by 2005, they were now about to attack Autobot City.
This would be the beginning of the end of the war
Years after G1 cartoon
It had been a little over 15 years since the G1 movie which Megatron became Galvatron, Shockwave was killed by Unicron, Autobots had won the war and Soundwave was on the run.
Soundwaves programming had now began to unravel
Soundwave was becoming Kaori Miyazono again.
First Soundwave realised that his old memories were returning, not as Soundwave, but as Kaori Miyazono, her memorable and mostly trivial times with Kōusei Arima like when they sung twinkle, twinkle, little star or when they jumped off courage bridge together.
Rumble and Frenzy started noticing that when Soundwave would have these flashbacks, a tear could be seen from his visor, Also at times Soundwave would start screaming "KŌUSEI ARIMA, COME BACK TO ME" and this would make the cassettes uncomfortable.
The Decepticons had been destroyed, Galvatron was captured, Scrouge and Cyclonous returned to become Thundercracker and Skywarp again and were given pardon by the new Autobot command, the rest of the once proud Decepticon army scattered across the galaxy, either captured, killed or on the run.
Soundwave decided to try and see Kōusei again and decided to fly to Towa Japan, However with low fuel, he ended up crashing in a petrol station on the outskirts of Towa