I just brought the hi-res version from
Mora.jp and did a listening comparison with iTunes lossy download. The differences are there but not dramatic. You definitely hear more details on the hi-res version, especially in the vocal range. For example, Airi's vibrato sounds very clear and smooth in the hi-res version, and at the same time Mai's voice sounds a little more squeaky at the B melody before the chorus. The hi-res version also has a little wider soundstage and a little smoother (sound less hash). But I think the hi-res version suffer from compressed dynamic range in the mastering. UF is more familiar in mastering music for personal audio used (i.e. earphone plug into a smartphone) which could benefit from a compressed dynamic range because small details need boost in volumes. However, hi-res audio has a lot more details, and with the same compressed dynamic you feel like all the details are squeezed into your head when listening at loud volume.
I would say buy it if you have hi-res gear. It is the same price as the lossy AAC version on Mora.jp, but iTunes is still cheaper. You need Japanese VPN to buy from Mora outside Japan. I used a free account from vyprvpn, and it worked fine. My US credit card also worked, but you can buy a Mora card from internet vendor and use it to buy from Mora if your credit card has a problem. Now, I am really curious about the vinyl release after knowing that they did the actual analog recording with no conversion from digital to analog.
P.S. The single is ranked number one in Mora hi-res download.
A side note. I hope they keep the hi-res release going for future release for other groups too. I am sure they will do a better job next time. But I cannot believe this is their first hi-res recording. Zetima is distributed by Sony Music, and I thought Sony music required all their recording to be hi-res or better since years ago. They invented the format anyway.