This one gets you in under a half hour, which is exactly why half the people who start it bounce off and the other half never shut up about it. It's a single-episode OVA carrying a full dimensional-travel romance on its back, and the wild part is that the rules actually hold. The mechanics of two people cut apart by time and space pay off in an ending that respects everything it set up, no cheating, no shrug. Yes, the animation swings hard between genuinely lovely and visibly rough when characters have to move, and yes, the scope wants a series it never got. Watch it anyway. It's quiet, it's patient, and it lands the emotional hit that shows with ten times the budget keep whiffing. Slept on by everyone except the people who found it.

After Mount Fuji erupts, ash covers much of Japan and keeps drifting down like snow. With another eruption expected, many people have fled, but some remain behind, spending their days mostly indoors. Rui Satou, a high school student among those left, looks for friends online between classes. He grows close to Michiru through their chats and resolves to meet her face to face, even though she lives nearer the danger zone. Their meeting reveals a bond far stranger than he expected, as two people split by time and space work through their tangled past before the world ends. The single-episode OVA blends drama, romance and science fiction.