As others have said, this was crap.
There's a comment above that says they liked the ending and that this was better than another work. It's fine if you like the ending. But saying this is better than another story doesn't mean anything. Both can be bad, even if this is just less worse.
Let's go over the ass pulls.
There's the obvious Mit-tan still being alive and her parents lying about it.
There's the obvious Sahara still being alive and his parents just conveniently doing the same thing and also lying about it, even though it was never hinted at before.
There's the teachers going along with the lies too.
But let's go even further and explain more. Mit-tan has finally woken up from her coma after like...a decade? Just conveniently waking up now, of all times. A month after Sahara woke up.
Also, it was a hit and run, and the driver was never caught? I honestly don't remember if it did ever say hit and run specifically before, but I don't think it did. I thought it had said accident. So the author just tries to shove the responsiblity on this nameless, faceless figure.
Then there's Chiaki. In the span of one single chapter with a flashback exposition dump, we get her whole backstory. Her grandmother told her to always smile. Herp derp, that's why she also smiles at Sahara's "death".
Anyways, there were a lot of problems. The author tried to make Sahara the main viewpoint, and he's also an unreliable narrator/viewpoint. He has flaws in his memory and couldn't accept his own actions. That's understandable. But the author went too far into bullcrap and just made him...pointless. He even says it in this chapter. If not for him, none of this would've happened.
This series was pointless.