They say that a spirit sometimes appears on a certain crossing in town. One day, a high school boy named Sahara gets into an accident on that very crossing, causing him and his friends' lives to change forever. (From Nameless)
3 Volumes (Complete)

Author used two writing techniques that I don't see often:
Decoy Protagonist
Unreliable Narrator
It was alright, everything got explained at the end. Didn't think there was any actual plot holes, but if you missed any clues it could seem like there were some. Some reasoning was a bit weak at the end, though.
One particularly important early clue was when
Kenta destroyed a memorial to Sahara on the ground. This ends up being a big clue connecting to the reveal that Sahara didn't actually die. He had no reason to do that unless he hated Sahara, or he saw it as an insult to his old friend who wasn't actually dead.
The late story reasoning that I thought was weak was
when the parents decided to lie about their respective child's survival, ostensibly to protect others from having their hopes dashed if the child didn't survive treatment in the hospital.