FANTASIA X THEORY!!
[warning: much long, very confuse. Thank you @ePanda_10 for your brain cells]

TLDR: @OfficialMonstaX are trapped in an hourglass shaped mess of time & space/dimensional travel. They are trying to return to the centre of the hourglass (ie 514) to be together.

Assumptions for the whole thread:

ASSUMPTION 1: 514 keys affect user and immediate surroundings (ie allow dimensional travel with collateral effect on time)

- SN + HW disappear but their surroundings are unchanged except for the rain/water

ASSUMPTION 2: Lighters affect people but not objects (ie stops progression of time for people but overall timeline continues)

- JH froze security guard but could still pick up keys

- CK froze cafe patrons but watch continued to make ticking sounds

ASSUMPTION 3: Music Box Keys (MBK) affect objects and surroundings but not the user (ie affects whole timeline except the user)

- MH and KH do not age or de-age

- Candles re-light, cobwebs disappear, cup un-shatters, clouds and sun move backwards.

POINT 1: THE HOURGLASS REPRESENTS TIME AND SPACE

In the FOLLOW logo, the bottom half of the hourglass is reflected through water. Time travel is heavily associated with water.

- Dramarama HW in the rain

- Find You HW falling through water

The hourglass' bottom half represents time disturbance, while the top half represents space/dimensional disturbance. The hourglass' centre is the only place where the members are in the same time and space.

Sand falling vertically through the hourglass represents time passing

But where at the members in this hourglass?

JH gives SN and HW the 514 keys to teleport (ie messing with space), so they are in the hourglass' top half.

KH, MH and CK are in the bottom half as they are messing with time.

POINT 2: THE ROOMS EXIST IN/NEAR THE CENTRE OF THE HOURGLASS

We know that there are 2 rooms. One is the 'storeroom' where JH takes the keys. We assume the lighters also came from the same room since their location is not specified. We also see KH get the MBKs from this room.

Both KH and JH have entered the storeroom, meaning it exists in a space and time that is accessible from both sides of the hourglass (somewhere within the solid gold star).

Presumably, CK has also entered the same storeroom for his lighter.

The other room (the "waiting" room) is where CK sits at the end of his teaser and in KH's teaser. This room houses the music box and the mantle clock.

As only CK, MH & KH enter, it is likely in the hourglass' bottom half, close to the centre where their timelines almost overlap

POINT 3: THE TOP HALF OF THE HOURGLASS IS THE WRONG PLACE

@OfficialMonstaX's aim is to be at the same place and time. JH, SN & HW are in the same time but different dimensions. JH steals the 514 keys and delivers them to SN and HW, attempting to bring all 3 to the same place.

This inadvertently removes SN & HW from their timelines. SN's car is rained on + HW's phone box is wet after they disappear, implying time travel is a side effect of dimensional travel as they cannot move in space without also moving in time ('location' is both a time & a place)

It is unclear whether JH succeeded in bringing all 3 to the same time and place. We DO know that JH's attempt sent them through both space and time.

POINT 4: THE BOTTOM HALF OF THE HOURGLASS IS THE WRONG TIME

Essentially this is a sh*tload of time travel. Initially KH went to the storeroom and took the MBK frame (necklace + bracelet). He then went to the waiting room to meet MH (sleeves = grey/black suit, CK = white shirt).

KH only took the key from the bracelet; MH left the necklace. They parted ways and travelled down their timelines on the hourglass. On CK's (stolen) newspaper, both necklace + bracelet are there but the bracelet key is missing.

About CK: We don't know if CK or JH took the first lighter but CK has a lighter which he uses at the cafe to pause time & steal a newspaper. When he finds out one MBK is missing, he goes to wait for KH & MH by pausing himself with the lighter (he doesn't move in KH's teaser).

When KH arrives at the waiting room, he realises CK is frozen and turns back time using his MBK. He goes back too far, to the time where he & MH originally met (CK is gone, since KH looks back to the chair CK was sitting in with sadness before MH enters).

This time, MH takes the necklace. He comes back much later (the room is abandoned/in shambles) and tries to go back much further in time. The time disturbance is on a much larger scale than KH's (sun + clouds move).

POINT 5: CONCLUSION (or lack thereof).

All we know is none of @OfficialMonstaX have gone where they wanted to go, which is back to the centre of the hourglass, to the time and space they can all be together.

@ePanda_10 is the only reason this thread exists. Ily