Tanjiro is the main character from the Demon Slayer. Tanjiro is the main character from Demon Slayer.

Tanjiro is the main character from the Demon Slayer. Tanjiro is the main character from Demon Slayer.

His mother, older sisters, and brothers are killed by man-eating demons. His mother, older sister, and brothers are killed by man-eating demons.

I think only his older sister is killed, right?

Only oneHowever, one of his sisters, Nezuko is, survived. However, one of his sisters, Nezuko, survived.

I made it a little more natural sounding, but a minimal change to make it "correct" would be: Only one sister, Nezuko, survived.

Only one sister, Nezuko is, survived. Only one sister, Nezuko, survived.

Only one sister, Nezuko is, surviveds. Only one sister, Nezuko, survives.

He gets panicked, but immediately, he runs carrying Nezuko at first, but then immediately put her on his back and ran to see the doctor. He panicked at first, but then immediately put her on his back and ran to see the doctor.

I struggled a bit as to whether to change the tense of the overall recap to present tense because you are describing it as it is happening, but past tense works overall if it is consistent. The version I propose here flows a little better with that in mind.

He gets panickeds, but he immediately, he runs to see a doctor while carrying Nezuko on his back to see the doctor. He panics, but he immediately runs to see a doctor while carrying Nezuko on his back.

In English, it's natural to say "he panics" instead of "he gets panicked" or "he becomes panicked."

But then, Nezuko suddenly triesd to bite him. But then, Nezuko suddenly tried to bite him.

Keeping with the "it is typically more correct to keep one tense" honestly though English is flexible about this in a casual sense and I am probably being pedantic.

This is how Tanjiro meetst Giyu. This is how Tanjiro met Giyu.

She ishad somehow transformed into a demon. She had somehow transformed into a demon.

This is a tricky one to describe the edit. In present tense, is technically works here, but it sounds like it just happens right then in that exact moment which isn't the case. Though since I moved everything to past tense, it works itself out. You also could do a heavier edit to say: "It seemed that she had somehow been transformed into a demon." This sounds a bit more natural. To me at least.

She is somehow transformeds into a demon. She somehow transforms into a demon.

When Tanjiro is attacked by Nezuko, Giyua stranger named Giyu suddenly showsed up and savesd him. When Tanjiro is attacked by Nezuko, a stranger named Giyu suddenly showed up and saved him.

The person you are describing this to doesn't have context for who Giyu is so it can be confusing. I wanted to put "a man named..." at first, but then remembered he is like 14 or something and "a teen named..." sounds silly in English even though it is correct grammatically.