Classification query: Springloll

Is this music indie or is it mainstream? Those categories give very different readings, but I really don't know. (Where but in indie do you get away with those wan sketchy vocals? The answer could be: in plenty of places.)

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[Poll #1666585]
(Also haven't determined if the spelling is Springloll (one word) or Spring loll (two words). And I prefer "주문을 걸어" - which Google translates as "Cast A Spell," a mainstream-seeming song title - to this song, but I couldn't find a video for it.)