Bl stories mixed with other genres (Adventure / Horror / Comedy...) -> ⚔☠

-> Mystery / Killer

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I loved that story but Wtf ?? The ending was so abrupt.
Well still a good story, but the ending is not my favourite

Can be seen as a sequel to the story "Song of Reverberation".

What connects the 2 stories is that they happen in the same world, but "The Promise" happens on the underground and "Song of Reverberation" on the surface.
Plus Jing ye, the Male lead of "the promise" is younger, and a side-character in "Song of reverbation"