Though the established characters are familiar with their own SEKAI, Broken Sekai is vastly different and is falling apart in an upsetting fashion.
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A blackout occurs in the real world, disrupting all electronics and transportation. This was caused by the Broken Sekai hitting its limit. Miku's voice also vanishes from the real world until the climax.
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While not the same thing, a phone that Broken Miku inhabits is thrown at the wall and the screen shatters. She doesn't appear to be physically affected by this.
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We're briefly led to believe that the Miku in each Sekai is dead. This is resolved in the climax and they're brought back.
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Vehicles are inoperable during the blackout, even those currently in use. No crashes are shown to have happened.
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Aside from the established game characters, some of the people that Broken Miku tries and are unable to reach act in ways that could imply some mental illness.
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When the Broken Sekai reaches its limit, the darkness of the sekai breaks free and infiltrates the other sekais, taking their respective Mikus. Miku's voice also vanishes from the real world.
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It will depend on what's considered a "priceless artifact", but there are a few scenes where a sculptor destroys their statue, someone deletes a picture of them and their friends off their phone, etc. These are all quite brief.