This is actually a really nice film once it gets going, but it takes a while to get there.
I've never seen a film get carried solely on one actress's smile like the first half of this film does. That's about the only thing that kept me watching through the first half.
The premise is utterly bonkers, and the whole first half of the film is dedicated to introducing that premise. The dialogue is clunky, and at the start you have to suffer a lot of "I'm a weird elusive girl but you'll just have to get with the program and follow me" moments which gets exhausting instantly. I found myself getting quite annoyed by the main female at the start, rather than curious about her. The English translation also sucks, which makes conversations confusing. And the side characters are mostly lifeless. If they spent less time on introducing the premise, this bit might be more bearable. Although once you get further on you might appreciate why they chose to do that.
It does pick up later. Seeing the 'home video'-style bits on Youtube are how I first heard of this film, and those are certainly highlights. Pretty, cute moments captured in that style, or sweet rendezvous scenes on bridges or rooftops. That's where you'll get sucked in.
The longing tone sets in late, but it overpowers all the clunkiness or annoyance you suffered in the first half. It even threatens to get philosophical at parts. Ultimately this film did manage to move me, despite irriatating me at the start. And you realise the actors are both good by the end too. Sweet film overall, if you're patient.