#mizuha

Immediately jumping down like that is a bit of an overreaction, no? Fushi has seen Hayase's reincarnations six times already. It's such old news that they didn't even bother getting out of bed when they met Kahaku for the first time (by the way, the frame of him in the OP is from that exact scene, haha). It shouldn't be a surprise to see that the lineage is still alive and kicking five hundred years later.

But... Fushi is surprised. For some reason. They actually have to get close up to Mizuha's face and stare at her in silence long enough to make it awkward before they can finally believe it (in the manga at least, in the anime they're an appropriate distance—though that's just because Mizuha immediately backs away when they try to get closer, ahahaha).

This isn't just a mild "oh, so Kahaku chose to reincarnate?" level of surprise. This is so disbelieving that they need to actually double-check to make sure. And their initial reaction after verifying Mizuha's identity wasn't to smile and ask how she was doing. It was this face:

When asked what they were going to do about Kahaku at the end of the Renril arc, Fushi said this—

—right before they went under. There was no time to go meet with Kahaku before the timeskip. They didn't even try, even though at this point they had already decided on going to sleep until they eradicated all the knockers. Isn't that indirectly admitting that they were planning on having the conversation after they woke back up?

Keep in mind Fushi hasn't actually seen any of their friends yet, apart from March. They've just assumed that they're all doing fine—and that they all chose to wait those five hundred years for the world to change. So, within the story's timeline it's entirely possible Fushi just assumed they had resurrected Kahaku and didn't notice otherwise until running into Mizuha. And really, why would they have to worry about the guy who said he would always be by their side?

I repeat, why would they have to worry about this guy? There's literally nothing to worry about. It's fine. Just trust him. It's probably fine.

When you look at it that way, running into Mizuha by pure coincidence was probably kind of a gut-punch. Anime Fushi genuinely sounded happy that she was happy with nothing else getting in the way but at the risk of sounding like a conspiracy theorist I 110% believe manga Fushi had... mixed emotions. Look at these expressions:

There's a hint of melancholy in there. Kahaku has been granted the posthumous title of "someone Fushi used to know." That's probably the most tactful thing they could have said, but still. Wow.

I guess whether or not Fushi actually tried to resurrect Kahaku like the rest of their friends is a little debatable. Maybe they had just hadn't gotten around to bringing him back yet. But they are in fact so shocked at seeing Mizuha's face that I would completely believe that Kahaku's empty body is decomposing in Yanome somewhere. Good angst material, if anyone wants to take that and run with it. Hell, I might do it myself.