Star Guardian, but a Darkin Blade

My name is Kevin. I'm 17 and a student. I have a normal outlook on life and the world, and even if you disregard the fact that I'm a reincarnator, I'm still just an ordinary nobody. This is an ordinary world, yet in certain ways it casually reveals that it isn't. For example, why is Viego my biological older brother? Why is Gwen Isolde's biological younger sister? And why is Lux one of my childhood friends... one of them, anyway! Sometimes, a few colorful stars inexplicably descend from the night sky. What do they mean? It took Kevin a while to figure it out: League of Legends, but in the Star Guardian universe. But why am I not a Star Guardian? Then one day, Kevin came across that sword: Aatrox.

[I will keep living. I will keep waiting. I will call out again and see who comes next. Unless you are worthy...]

[You mean... if I possess you, I can build a harem here?]

[...Is something wrong with your head? Just go. I'll wait for the next person who's meant to find me.]