1theK put up a music video titled "[MV] JUEUN(주은) _ Heartbeat(너랑 나는) (Feat.SHIRT)" at 18:00 KST on August 9, 2026. It runs two minutes and six seconds, and it went to the distribution channel rather than an artist channel.
At the time of writing the upload had drawn 1,000 views, with 102 likes and 11 comments. Under it there are no production credits and no separate credit line for either name — the only credit anywhere on the post is the one printed in the title, "(Feat.SHIRT)".
What the description does carry is 1theK's standing block: a welcome line, a link to a "1theK Live" channel, and this notice, given in English on the post — "1theK YouTube is also an official channel for the MV, and music shows will count the views from this channel too." It closes on the tags #NEWRELEASE #MV #1theK.
Past that block the description is empty of the things you would normally go looking for. There is no release-date line, no producer or director credit, and no link to an artist account. Nothing in the post says anything further about the collaboration beyond the credit in the title.