Akuyaku Reijou ni Nanka Narimasen. Watashi wa『Futsuu』no Koushaku Reijou desu! - Chapter 192.2: It’s scary when a gentle person snaps.

The aliens came with hostility.
Facing the invasion of aliens, human beings are weak like ants.
So this is the end, the real end.
But there is resistance when there is an invasion.
For some, this is not the end, it is war.
So this is war.
Real war!

- Description from Qidian

Amamiya Hiroto is unlucky. His life consisted of misfortune after misfortune, culminating in an unlucky death during an incident on a school boat trip, trying to save a girl he barely knew. After death, he met a god of reincarnation who requested that the hundred or so dead passengers—one of them being the girl he tried in vain to save—be reincarnated into another world.

After the fall of the Galactic Federation, long-time lovers Lu Li and Xie Jianwei defeated the alien invaders, and formed the Empire with Lu Li as marshal. Everyone thought that all was well between them, but.

Xie Jianwei one day found out that Lu Li’s personality had split into several parts.

They were all individuals, yet still the same Lu Li. How could Xie Jianwei bear to watch as each Lu Li plot to kill the other?

Xie Jianwei used his SSS-class spiritual strength to enter Lu Li’s inner world, where Lu Li was god/director/actor all in one. To get to the bottom of the mystery, Xie Jianwei had to act along Lu Li’s delusions, else the dreamworld would collapse, worsening Lu Li’s condition, and split the personalities even further.

- Description from Novelupdates

It was only after Su Yayan's death that she realized that she was a malicious cannon fodder female character who became a scapegoat in a Mary Sue story.