[GoseiWonder]

All the people across time who ate Helheim's fruits, sealed in some kind of cocoons (either being wrapped in vines or more like a pomegranate seed), all ready to be woken and freed.

What really pushed Micchy into agreeing with Takatora was that their parents were cocooned and what ever "Helheim' Choice" and Yggdrasil's true goal are, they are intertwined with freeing the people (and presumably one mouse) from cocoons.

Yggdrasil itself doesn't care about the cocoons though, as freeing the people from the cocoons is a fortunate side affect of whatever villainy-under-the-guise-of-heroism Yggdrasil is planning.

Is it unrealistic? Yes. Plausible? No. Make sense with Micchy's reaction? Not really. Schmaltzy and Deus ex Machina-y? Oh hell yeah. Do I care? Not in the slightest!