I totally don't remember the title, but, I clearly remember the plot.
It starts with the guy and a little girl, the girl is the strongest knight and the guy is the weakest person in their village. The guy is the little girl caretaker, he helps her with shower, clothes, and many other things.
In the middle of the chapter, the guy was feeling skeptical cause he can do anything for her, but, he can't protect her. So, he kept training without her knowing, when he was training, he met his future self.
His future self told him that a demon king/lord is going to come to their village and the girl is going to get killed by that demon.
He was furious, his future self, knowing full well what the guy is feeling gave his power and memory to the guy. A few days later, the demon lord/king really did come to their village. The guy haven't realised he got his future self's power so he was just stuck with the memory of the girl dying it repeated in his head since his future self said it.
He was worried about the girl cause if she fights with the demon lord she'll die, but she's the strongest knight in their village, so she can't just ignore the demon lord/king destroying the village, but in the middle of their fight, the Image of the girl dying suddenly popped up in his head, without any second thoughts, he runs to the girl and tries to save her.
Right at that moment, his power from the future shows up and he's able to save the girl. A lot more things happened after that but I can't describe it very well