This review may contain spoilers. I can handle the truth.
No, high school kids cannot mobilise like that. It's not true. It's impossible. It can't happen. I refuse to believe it. You're wrong. It's fiction.
(Features the most hilariously convenient third-act twist I have ever seen. Umi and Shun fall in love and then discover that they're siblings, subsequently spending the entire movie desperately trying to not fancy each other until they both go fuck it, let's go out anyway. And then THAT SAME NIGHT Umi finds out that they're not in fact related. Phew! Thank god for that amirite?! Absolute galaxy brain Goro.)