Kid Cudi was not depressed, for a change. In a sparsely decorated modernist SoHo apartment, purchased with money earned from his hit single “Day ’n’ Nite,” Cudi fiddled with new toys. A vaporizer, a lightsaber, a chain wallet, buttoning and unbuttoning the flap with the nervous energy of a meerkat. The spoils of a young rapper in skinny jeans. Born Scott Mescudi and raised in Shaker Heights, Ohio, Cudi rarely projected exuberance as an artist, but on this day in 2010, he was giddy. He had things to look forward to.

Cudi and I spent several hours talking that day — about accusations on the internet that he was using liquid cocaine (“that shit makes no sense”), about rumors that he had threatened his girlfriend (no formal complaints were made), about paying for studio time by working shifts at Applebee’s (he amiably waited tables), about the death of his father when he was 11 years old, about working with his mentor Kanye West, and about the excitement around his new album, Man on the Moon, Vol. II: The Legend of Mr. Rager. The profile born of that album cycle portrayed a pugnacious but cheery young man, just 26, figuring out how to be famous without abandoning “the lonely stoner” persona that had made him relatable to thousands of young fans. I spoke with Cudi’s mother, Elsie, a dynamic and emotionally present woman who talked in great detail about her son’s vulnerability. I spent time with Emile Haynie and “Plain Pat” Reynolds, his then-managers and the coauthors of the woozy, antic Kid Cudi Sound. Haynie and Reynolds spoke about their liege with a worried anxiety. Both were true believers, but they had a delicate artist on their hands and had been feeling wistful for the previous 12 months. “The come-up is always the best part,” Reynolds told me. They knew it could turn at any moment. It did, eventually.

But before it did, Cudi complicated rap’s notions of identity. Ravers and thugs alike aped “Day ’n’ Nite,” which was picked up by Hot 97, WTKU, and K-Rock 92.3, a rare trifecta in New York radio’s heyday. He enlisted Common to narrate his debut and teamed up with Steve Aoki and 3OH!3. Before Drake and the meme-ing of rapper emotions, Cudi expressed sweeping feelings of sadness and rapped about drug use with directness (“Doin’ bumps in the day and keep blunts to burn,” he rhymes on “Wild’n Cuz I’m Young”). The recorded snorting sounds on “These Worries” are as performative as they are unnerving. His songs sampled MGMT and St. Vincent and Ratatat and Lady Gaga, positioning himself as both inclusive and pretentious. He hooked up with Haim and Father John Misty years before many knew who they were. If you scan his playlists on Spotify, you will find several songs that would seem comfortable on a soft rock drive-time set: songs by Coldplay, Keane, David Gray, the Red Hot Chili Peppers, and others. Cudi is not a snob — after all, he did appear in How to Make It in America and Need for Speed — but he is vigorous in his taste. And sometimes that taste is dreadful.

He’s also an artist who thrives on atmosphere — he literally sounds better when you’re high. The most important Kid Cudi lyric is wordless and infinite. It appears on nearly every song he has ever recorded — it is one part ad-lib, one part sonic bridge. Hrrrrrrrmmmmmmmmmyeeeaaaahhhhhhh, he intones like a bothered hippopotamus. It’s a rumbling, dewy cry that’s either lazy songwriting or one of pop’s keenest weapons — think Paul McCartney’s artful deployment of the “Yeah, yeah, yeah” refrain. You can wedge it anywhere into one of his songs — the opening ticks, the chorus, or, typically, the bridge. It’s what connects him to his artistic father.

When we met, Kid Cudi was in the early stages of presiding over one of modern rap’s first #hives — he was a nationally prominent musician who also happened to have a subdivision of irrationally dedicated fans. Cudi fans tend to resemble ’80s goths — dour, sarcastic, cloaked in dark uniform, existentially wounded — only they read Complex and have exceptional taste in Jordans. His fan base was introduced to a certain kind of rap stardom by Kanye West. Cudi took many other cues from West, stylistically and also temperamentally. Both were prone to bratty outbursts, wild clusters of creative activity, curious collaboration, and stilted wordplay that somehow made them seem more human. Kanye was the chief orchestrator, but Cudi distinguished himself as a melodicist of uncommon talent. For a spell, they were a thrilling pair — Kanye, who made Cudi one of the first artists on his G.O.O.D. Music imprint, oversaw Cudi’s first album, while Cudi supplied songwriting and vocal guidance for several songs on 808s & Heartbreak, an album that has become a totem for many young rappers. Kanye cosigned, Cudi cowrote.

Earlier this week, Cudi lashed out at Kanye, claiming that West (and Drake) “don’t give a fuck about” him. It was a slightly illogical but authentic meltdown — a Cudi specialty. Since I met with Cudi, his career has taken strange turns. His visibility as a major artist has declined, but he has been productive, releasing three albums with a fourth, rumored to be titled Passion, Pain, and Demon Slayin’, on the way this month. Cudi has pursued some of his more eccentric interests, including a fascinating and often unlistenable alt-rock side project called WZRD with the producer Dot da Genius. His albums under his own name have become increasingly rock-oriented, and dissolute.

Last year’s ramshackle, bloated Speedin’ Bullet 2 Heaven — a truly baffling release — recalled a humorless Nirvana cover record. There is a song on the album called “CONFUSED!” Cudi is making his music, but he doesn’t seem to be all there. Last year, he appeared in the painfully intimate independent film James White, playing the supportive friend of a struggling New York man grappling with the loss of his father and his identity. It’s hard not to see the parallels.

Still, when I attended the Coachella Valley Music and Arts Festival in 2014, Cudi commanded the single biggest audience I have ever witnessed in a live music setting — approximately 50,000 people, more than half of the attendees — gathered for a sundown set at the main stage to watch Cudi moan, rock, wail, and vibe out to the Crookers remix of “Day ’n’ Nite.” It was an ecstatic sight that I still do not understand. Cudi smiled and danced throughout his hour-long set. Later, in the VIP tent, I spotted him quietly sipping a Corona, seated alone.

Cudi and Kanye grew apart. Cudi went inward, and Kanye went out, becoming a bigger celebrity, a bigger artist, a bigger voice. Cudi found his people — young and amenable to his radical vulnerability. Kanye found Kim Kardashian. Cudi became a father. Kanye did too. The many children West “birthed” — as he said during a reply to Cudi at a concert on Wednesday night — before his actual children, Saint and North, have grown tired and frustrated with their father figure. The list of West expats — primarily his songwriting collaborators — is long and dismaying. It includes Rhymefest, Consequence, and an on-again, off-again relationship with Cyhi the Prynce. Kanye loves to build a farm team — he’s presently overseeing a widening crew, with the additions of Migos and Tyga to G.O.O.D. Music, along with the emergence of Desiigner as a potentially vital artist and Teyana Taylor as a manifestation of physical power. But he struggles to manage his prospects. And there’s room for only one temperamental genius.

Still, Kanye and Cudi belong together, father and son. I think often of the gorgeous bridge from The Life of Pablo’s “Father Stretch My Hands Pt. 1” — at the height of one of West’s most thrilling recent musical moments, there is Cudi, exclaiming, “Beautiful morning!” That song appeared just a few months ago. Cudi now finds himself at a crossroads, bridge burnt behind him. He has a devoted base but little chance at national reclamation. He is making ponderous music with old collaborators. Will he continue to recede from view, ever the self-imposed outcast?

I saw Cudi one more time after New York and Coachella. It was at the well-known Los Angeles Italian restaurant Little Dom’s. It was the day after Christmas 2014 and he was there with his daughter, his girlfriend, and his mother Elsie. I said hello to Cudi, who did not remember me, but was polite. I shook Elsie’s hand. His daughter laughed and squealed through dinner. It is impossible and unfair to grade the emotional state of a person dining at a restaurant, but Cudi did not seem terribly happy. Not depressed, exactly, but almost as if something was missing. Like he’d lost someone, and didn’t know where to look for them.