Ah, what the heck. I've got time on my hands and nothing better to do, and although this passage is very short, I see a lot of ways this can be improved. Hope I don't seem like a backseat author~
So uh, first of all, even though it's short, this passage needs some indentions. Spacing. When you break up the text into paragraphs, not only is it easier on the readers' eyes, but it also helps with the flow of the story, too. It makes transitions a little less sudden and awkward.
"Destinies are never known, so they can change. Hearts are separate from one another, but they can beat as one. Being connected with other hearts determines our destiny."
Like, right here. I would start a new paragraph right after this, adding a space between that...
It all started with that day. I've always wished it was just a dream, and endless dream I would eventually wake up from. I'll never forgive myself for not saving him, I've failed. I'm sorry I couldn't save you.
...And this.
Though looking at this, you might either want to elaborate on this idea before launching into the rest of the story, or omit it altogether. It seems odd for someone to be talking like they're recalling past regrets, only for the narrative to abruptly abandon that angle and just start telling the story. Buuut if you feel like keeping it, it would be good to start a new paragraph there, too. Make the transition a bit smoother and all.
Oh yeah, you should always start a new paragraph after dialogue.
Muke looked at me with a look of disappointment on his face.
Maybe add a little more variety to your word choice. Take out the modifiers and nouns, and you're left with the phrase "looked with a look." Sounds kind of awkward, doesn't it? There're a lot of fancy ways to rephrase this, but the simplest would be to use another word for "looked." A thesaurus is your friend in these situations!
Anyhow, like KitKat said, it might be better if you posted more content than just one paragraph at once. Your story certainly isn't bad, but there's not really enough
there for me to say with certainty that it's good, either. Keep the story coming, and I might have a stronger opinion later on.