
Same when I started reading this I was like- wait hold up- how come the cover him and the actual him look different?? I came to the same conclusion that I think he becomes a shinigami too.
Or we could just be reading into things, it might just be that the cover him looks different. Could be him when he was a child? He looked pretty when he was six.

Ya idk. When I first clicked on this I thought the boy looked really pretty and I was kinda expecting the shinigami to look like Ryuk from death note.. I was really happy when I saw that Caleb looked normal
Maybe the hands are his final form and he just puts on his human form for Eiji?
Or like you said the cover was to draw you in or just a completely different cover.

I put what is on the cover into a search and a product page came up on Amazon JP. There are six volumes of that anthology. I looked through the previews of the kindle version. Each volume has one chapter of each manga. This manga is one of six different manga that's in the anthology. I have no idea which manga is in the cover though, I couldn't really tell. It may just be art created specifically for the theme.
I think Eiji will die. Because I feel like the Eiji on the story and Eiji on the cover is kinda different. Maybe we will have those clichè ending where Eiji die and reincarnated and still remember Caleb so they can have happily ever after.
Or vice versa. Caleb die, maybe Eiji too, and they meet again in the next life.
But, again, seeing the cover with feels-different-Eiji and a dark hand, I think my first guess is the closest one.
Can't wait for the next chapter anyway(づ ̄ ³ ̄)づ