I think I have read an English-scanlated sci-fi manga a long time ago but I don't remember the title.and as far as I remember, I have read the first two chapters.
But I can give a description with the details that I did remember.
A teenage boy who witnesses a sudden alien invasion over the city. Some weird spheres pop up and encase them inside. The boy manages to avoid the sphere but loses his arm. Instead he gains a new super power. He meets a girl who lost her leg to a sphere. but gains a new power. Her leg has power to burn with fire.

Would anyone please tell me the title of the manga with the details I have described?

This might be Hiniiru, although it's not sci-fi and the events there were somewhat different.

Quote from ImmLff

This might be Hiniiru, although it's not sci-fi and the events there were somewhat different.

But you are correct. Hiniiru is the title I was trying to remember. Thank you very much for refreshing my memory, sir.

I didn't remember much about the manga that I hadn't read in a long time, so that is why I was really mistaken about the genre being sci-fi.