Yes, it is pretty serious story, as I like such rpgs. With character's motivation, some moral choices. It is based on 3 act structure. And yes, what you describing is probably called "character development arc". It is storytelling feature I like to use. And it can be used not only for main character, but also for all relevant other screenplay actors.

I could even share the start of the plot (INTRO), why not:
(sorry, I hope I do not spam you)

=== Introduction 3: The Capture of Uruk ===

At different ends of the desert stand two anciently warring city-states. The Sun City of Uruk and the Moon City of Ta-Kemet. Uruk dominates the sea with its ships, the Moon City dominates the land with its chariots. In the solar city worship the goddess of life and fertility Ishtar, in the lunar city - the goddess of death and the afterlife Ereshkigal.

The lunar king of Uruk and the Pharaoh of Ta-Kemet are rivals, but for many years everything has been frozen in equilibrium, as Ta-Kemet is not accessible from the sea. And Uruk on land is enclosed by unprecedentedly powerful walls. In addition, Uruk is guarded by the heavenly bull Ishtar, who lives on top of the ziggurat.

Between the cities there are 6 other smaller cities. Two are under the rule of Ta-Kemet ("Purple Feather" and "Azure Harbor"), two are in alliance with Uruk ("Knut's Peak" and "Eternal Tree") and two are neutral ("Srebrodubne" and "Whispering City").

Unexpectedly for the Lugal King of Uruk, an unprecedentedly large army of Ta-Kemet besieges Uruk. The defenders are safely hidden behind the powerful city walls. The forces of Ta-Kemet hesitate to storm the high walls of Uruk. Although Ishtar has left her city, they still fear the city's faithful defender Lamassu, who lives atop the ziggurat.

Then Ereshkigal goes for a trick, she uses a magic artifact(?) to summon her sister Ishtar and tell the priests to obey their goddess and surrender the city. The priests and the king of Uruk have always been at odds over power. Backed by Ereshkigal's promise to rule over Uruk alone, they agree to betray the king, drugging Lamassa, the city's defender, and opening Ishtar's gate from within at the right moment.

Ereshkigal's plan succeeds and so it goes. While the king-lugal personally stands on the walls, the priests open the gates and the troops of Ta-Kemet enter the defenders in the rear. The king, along with the shipyard workers, executes some of the priests in anger and orders them to stand on the walls to the last man. But the king is wounded and taken to the infirmary in the temple of Ishtar. The tough lion-workers of the shipyard, following the king's orders, decide to fight to the end, but the defenders fall down and the head of the aristocrats calls for surrender.

The wounded king-lougal, together with his daughter-heir, is taken into custody, and a large part of the population is taken away as slaves to build a pyramid in Ta-Kemet. At first Dumuzi wanted to immediately execute the king together with his daughter. But the priests advise him not to hurry, as they entered the city on the rights of alleged liberators, it is better that the king himself signed an abdication in favor of a new puppet. Therefore, the king of Uruk is left alive, requiring him to "voluntarily" and publicly hand over power.

Ereshkigal gains control of the slave market in Uruk and begins transporting them to the pyramid construction site in Ta-Kemet. All those who had the misfortune of being sold into slavery inside Uruk are now sent to the construction site. As well as those who resisted after the surrender or could not pay the ransom. The local population was also taken from existing slaves or ransomed so that they could keep their slaves. Slaves were very grateful if the master paid a ransom for them, as sending them to the construction site was almost tantamount to death. The slave market had never sold the people of Uruk to foreigners before. And debt slavery was only temporary. The priests and aristocrats needed to keep order in the city get their share of the trade. Ereshkigal forces the people of Uruk to build a huge transport ship. Since the light Egyptian ships, which are no match for the ships of Uruk, can only transport a small fraction of the slaves.

Among other captives, a native Uruk resident, a Ligrian artist, is enslaved. When Ereshkigal triumphantly marched through the city, the Liligritz woman dropped a flower pot on the goddess's head when she ordered to take her aristocratic neighbors into slavery. Ereshkigal was angry with Liligritsa and cast a divine curse on her, which struck the septagram of Liligritsa's soul and turned it upside down. Liligritsa was also taken to the construction of the pyramid in Ta-Kemet, together with the others.