I'm kinda shocked and surprised that quite a few of us have already quickly realized that this is more
Mujaki no Rakuen time travel, and yet there's still confusion and discussion of how the time travel here doesn't make sense.
In case anyone forgot, Shouta leapt through time due some very intricate circumstances (has to be the right phase of the moon, where both Shouta from the past and Shouta from the future need to be in the same spot, and a bunch of other bleep that is easily forgotten), and in his variation, he clearly brings what he was wearing at the time to the past. Shouta even manages to change the future with decisions he made in the past, as shown when he saves Rio from the accident without getting hurt (This indicates that Uran likes the multiple timeline theory - after all, we have Shouta from a future where he's a Neet, Shouta being boyfriend to Rio {arguably the same one that led him to be a Neet}, Shouta being boyfriend to Sayo {drifts apart, but ends off relatively well}, then Shouta finally getting Konomi thanks to preserverance). Thanks to the same art style and everything, it wouldn't be too much of a stretch to say that not only is this story using the same time travel mechanic, but it also even shares the same universe as Mujaki no Rakuen.
In case anyone needs a TL;DR though: as anyone who's read Mujaki no Rakuen already knows:
The time travel mechanic is not important in this story. It's just a silly plot element, nothing more, nothing less. Most of us are really here to see Uran stuff.