Baka to Test to Shoukanjuu‎ - Volume 7, The Third Question

Awakening to a post-apocalyptic world infested with zombies and mutated monsters, Alex makes a startling discovery: he possesses a system that grants him access to unlimited resources every day.【Congratulations, you've received unlimited bottled water.】【Congratulations, you've received unlimited 9mm bullets.】【Congratulations, you've received unlimited cold medicine.】...With each system notification, Alex's chances of survival soar while others struggle to stay alive.As everyone else fights for their lives, Alex finds himself living in luxury, residing in a lavish mansion where he leisurely sips red wine and savors grilled delicacies amidst the chaos of the end times...

Transmigrating to the disciples of the Demon Sect, and relying on the skill modifier to become a giant of the Demon Dao.

[Detected the technique “Blood Nerve”, relying on devouring blood to practice]

[Side effects: easily affected by the spirit contained in the blood, becoming bloodthirsty, bloodthirsty, mad, and even brain dead]

[Please wait a moment, the system is being modified…]

[Ding! The modification is complete, and the side effects are cancelled]

- Description from novelbuddy

Struck down amid the battle, the Hero and Demon King meet their demise. As their souls linger on the edge of the afterlife, a mysterious force intervenes, merging their fragmented souls together with a new being. Rusty, the living armor, now affected by their memories and presence, embarks on his own quest. Will he seek revenge on those who betrayed the hero, or will he fulfill the desires of the fallen demon king? or instead, forge his own path?