Braggadocio is a foremost trope in hip-hop: rappers often boast about how much money they make, how many cars they own, how they run the game. Yung Lean isn’t like other rappers. “Yung Lean is like water: he’s always changing due to the temperature; how he’s feeling,” explains the rapper, referring to himself in the third person. “Lean could be on some Sid Vicious punk shit one day, and then on some heartbroken Justin Timberlake/Nelly Furtado shit [the next]. Lean just follows his heart wherever it wants to go.”

Lean – aka Swede Jonatan Leandoer Håstad – is a complex character; a persona that the internet was first exposed to in the beguiling video for his 2013 single ‘Ginseng Strip 2002’. Transfixed by the peculiar sight of an apathetic teenager in a bucket hat rapping in monotone about his emotional state, pills and scientist Alfred Nobel, millions of Tumblr users shared and exhibited wonder at this curious new artist.

The enigmatic nature of Lean’s breakout success (‘Ginseng’ generated nine million views, while signature track ‘Kyoto’ later clocked up 15 million) was driven further by the rise of the ‘Sad Boys’ movement – a name taken from the moniker that Lean and his producers, Yung Sherman and Yung Gud, make music under – with followers (both Sad Boys and Girls – they don’t discriminate) mobilising on internet forums in a rush not seen since Odd Future’s rise in 2011.

As NME checks in with Lean over Skype, he’s ensconced in his smoky Stockholm studio working on the next Sad Boys release, even though his second album, ‘Warlord’, only dropped back in February. “We’re always one step ahead,” he knowingly states about the collective’s strong work ethic.

‘Warlord’ takes on a heavier tone than his 2014 debut ‘Unknown Memory’, a direction typified by such lines as “Yung Leandoer don’t give a fuck about the fame” (‘Sippin’) and “I take what I got, I live ‘til it stops” (‘Miami Ultras’ – its accompanying video is a dark affair, depicting Lean alone, in a forest, wearing a dress and digging his own grave). “It’s ‘Yung Lean’s Dark Twisted Fantasy’,” he offers as a summation of ‘Warlord’, (mostly) referencing the title of Kanye West’s opulent 2010 album – although it’s much closer to Ye’s abrasive and electronic 2013 work, ‘Yeezus’.

Lean’s latest movements have certainly sustained interest in his weird and wonderful world, which may swell a little larger soon if certain rumours are to be believed. A Swedish hip-hop journalist claimed last September that Lean would guest on Frank Ocean’s long-awaited second album, and, while he doesn’t name any names, Lean does reveal that when he met Kanye producer Mike Dean in London they “were working with a famous artist together. I can’t say who it is, because he hasn’t released his album yet.”

That speculation can lie low for a little while, though, as Lean is currently mid-way through a world tour that visits these shores this week for three sold-out shows. The initial mass interest in Lean and the Sad Boys may have downscaled from viral phenomenon to a core fanbase, but clearly Lean and the Sad Boys continue to court a substantial audience wherever they go.

“I think [we] can go as far as [we] want – if that’s the goal,” muses Lean on what the future holds for the Sad Boys. “But really, it’s all about the love for what you do.” It’s a refreshing outlook that reinforces Lean’s continued separation from the more formulaic facets of hip-hop, ensuring that his unique outsider story is one that you can still very much delve into.

Yung Lean plays:

London Koko (May 6)
Manchester Sound Control (7)
Glasgow The Art School (8)