Nice! I don’t know Korean, but the singing sounds good in general.
I feel like the synth community needs to align with all other music communities a bit more though. I don’t think the two will be completely separate for long.
Tuning = adjusting notes from out-of-tune to in-tune. Not really required for a synth. Maybe “vocal editing”? “Vocal production”?
And, unless you got the isolated instruments from the instrumental, and adjusted their volume, EQ, compression, etc, on your own…I dunno about taking credit for “mixing”. Though that’s more of a grey area, since the vocal really does fit well with the instrumental, regardless.