Theory for Allegory.

Junho being the only member who had experienced being an idol has returned to the place where his brothers are yet to enter the world of being an idol.

When he finds the doors in the middle of the dark wilderness, he opens the box containing....

... a watch, as soon as he holds it, the clock starts again meaning he is getting another shot at being an idol. Then he enters the door, bringing that same chance to his brothers who are yet to debut with him. The time starts for all of them as soon as they open the box.

so like the wilderness is woollim's dungeon and the watch represents "our time is now" kind of vibe

There were no knobs in the doors from the photo teaser but when Junho appeared he opens a door with a golden knob. Similar color to the watch he has. It was like he is the only one who can open the doors (the knobs magically appear) which explains why the others are locked inside

Adding this here just in case I actually continue this theory for the next teasers.

D - DOOR
R
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P
P
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adding this here just because haha https://twitter.com/hyse0ng_petit/status/1302642387483672576?s=19