 If you liked
Arata naru Sekai: World's/Start/Load/End
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 ...then you might like
Mou Hitotsu no Mirai wo.
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"World's End" / "Arata naru Sekai: Mirai-hen" and "Mou Hitotsu no Mirai wo." are two short anime that each focus on a form of time travel via pseudo-science.
Though the tone and atmosphere are very different, the protagonists of both respective works are groups of good friends who do not seek out to do harm.