Miles wants his Great Perhaps, but we never really know what he envisions as his Great Perhaps and whether the boarding school of Culver Creek lives up to his expectations. Keep in mind, he's a junior in high school who is obsessed with the last words of dead people and has enough self-awareness to know that he won't find his Great Perhaps at home in Florida. This is our first big clue that there's more to Miles than the average teenager… and we're lucky enough to get the whole story from his skewed, snarky perspective.
But Miles isn't always a reliable narrator, especially when it comes to Alaska. His emotions, like many of ours, tend to cloud how he sees her, especially after her death. Eventually the Colonel yells at him:
"Do you even remember the person she actually was? Do you remember how she could be a selfish bitch? That was part of her, and you used to know it. It's like now you only care about the Alaska you made up." (13after.35)
Excuse the Colonel's language, but he stands to be the voice of reason for Miles after Alaska dies. Because Miles does romanticize Alaska. And we as readers have to watch out for what his grief does to the truthiness of his perspective.
"Miles is a great leader," said no one ever. In fact, he's pretty weak-willed when it comes to social interactions. He follows the Colonel wherever he goes:
"THAT'S THE POINT, SHERLOCK!" the Colonel screamed back. The ref came over and kicked him out of the gym. I followed him. (109before.47)
He does what Alaska tells him to do:
"What am I going to do?"
"You'll spend Thanksgiving with me, silly. Here." (58before.46-47)
And all his following and passive inaction (remember how he leaves Lara alone after their disastrous triple date?) leads up to the moment when he and the Colonel choose to let Alaska go. Indeed, Miles sums his passivity and powerlessness in the face of Alaska nicely when he states:
If people were rain, I was drizzle and she was a hurricane. (49before.32)
Miles will never be the force of nature that Alaska was—he just doesn't know how to make a big enough splash (so many bad jokes in one sentence—sorry/not sorry). But as he grows into the society that he's entered—the world of the Creek—he becomes a little more assertive, a little less like drizzle and a little more like a steady rain. Maybe some of the strength of character in the Colonel and Alaska is rubbing off on him.
He finally finds the courage to talk to Lara after Alaska's death (albeit almost two months later and with a nudge from Takumi) and he plays an integral role in the greatest prank the Creek has ever seen. Miles won't ever lead anyone, but that's because his strengths are internal instead of external like the charisma of the Colonel and Alaska.
Miles's introspective nature and introversion especially come to the fore after Alaska's death. For the Colonel, the world is fairly rigid: people are good or bad, he likes someone or he doesn't, he knows a country's name or he doesn't. But Miles's mind wanders along paths of variation, where nothing is rigid or clear, especially when it comes to who Alaska was and his role in her death.
For one, he has to contend with what love is and who exactly he loves. He loves Alaska. Or does he? Not only is she "the hottest girl in all of human history" (128before.81), he feels like he bonds with her on an intimate level. He spends Thanksgiving with her, he wants to innocently sleep with her (49before.32), and he comforts her when she freaks (44before.13-26). But whatever Miles does for Alaska isn't enough, and he eventually realizes it after the Colonel, in his usual brash way, kind of shoves it down his throat.
And if she were here, we both know that she would still be Jake's girlfriend and that there'd be nothing but drama between the two of you—not love, not sex, just you pining after her and her like, 'You're cute, Pudge, but I love Jake.' (20after.15)
While real talk like this might curb just about anyone's confidence—and Miles isn't exactly brimming with confidence to begin with—he somehow remains the eternal optimist. How? When he realizes that she didn't care as much about him as he wanted her to, instead of curling up and hiding from life, Miles opens his eyes to the other people who cared about her. And this helps him keep going.
The Old Man also helps Miles's brain keep churning. The lectures he gives in World Religions class often spark musings Miles has about life, death, and life after death (does it exist? Is it nothingness?). Miles was always kind of a deep guy before Alaska died, but afterward, the topics of World Religions become much more present in his thoughts after her death.
It's through these internal monologues (sometimes dialogues) that Miles is able to move beyond his immediate grief of Alaska's death to make some realizations about her, death, and himself. And in the process of these musings, he leaves behind his somewhat naïve vision of Alaska while retaining how much he cares about her:
I would never know her well enough to know her thoughts in those last minutes, would never know if she left us on purpose. But the not-knowing would not keep me from caring. (136after.10)
See? He is an optimist. This giving of self and disregard for the solution to the mystery of Alaska not only indicates a more mature love, it also implies an unequal love… which is okay for Miles. What? Don't we want to be loved in return? Well it's kind of hard when Miles realizes that Alaska is perhaps incapable of loving him:
I wanted to be the last one she loved. And I knew I wasn't. I knew it, and I hated her for it. I hated her for not caring about me. (20after.17)
But we know he doesn't hate her. And he knows he doesn't hate her. In fact, the way out of his labyrinth of grief about Alaska is forgiveness: for Alaska, for Takumi, for the Colonel, and most of all for himself. He tells us:
I will forget her, yes. That which came together will fall apart imperceptibly slowly, and I will forget, but she will forgive my forgetting, just as I forgive her for forgetting me and the Colonel and everyone but herself and her mom in those last moments she spent as a person. (136after.14)
It's in these words that we realize Miles's recognition of Alaska's selfish and suffering nature. And it doesn't matter to him—he loves her for who she was, for who she is to him.
And that realization might be worth the pain of grief after all.