"BLACK days, PINK nights" is a humorous fanfiction story. It's a story about the most dedicated Blackpink fan - Mr.HardcoreBLINK who accidentally becomes CEO of YG Entertainment. Originally it was published on the allkpop forum but later has moved on separate site.

According to the plot (

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about upcoming Blackpink's member solo. The statement fits in with the fanfiction plot for Rosé. The plot states she'll have a comeback first among the members, probably with a full album, but only after a group comeback. 

A series of coincidences make this situation funny.