He hesitates in a contemplating-a-quibble sort of way, but then nods.

"Meraiyu aisara leave Meraiyu, before Saikirei? Go other stars?"

He shakes his head.

"Meraiyu aisara..."

This demonstration is going to need a globe. He makes one. It's made of two different colours of wood, darker water and paler land.

He points to the continent that matches the shape of the depressing diorama that still stands in his room from that first conversation. "Meraiyu," he says. "Meraiyu aisara, before." Then the other continents. "Udimal, Lohei, Alaila. Meraiyu aisara go Udimal, go Lohei, go Alaila. Build small cities." He covers Meraiyu with his hand, and a pool of shadow flows and recedes, leaving the continent scorched to a darkness resembling water. "Meraiyu down. Small cities other place maybe live, maybe die. No aisara leave," he gestures to the globe as a whole, "place."

"Oh," she says, obvious comprehension dawning, and then - "Aisara above water, other parts place? Aisara live?"

He shrugs. "Above water. Maybe live. Maybe die. Saikirei can't leave Meraiyu, can't see."

"Saikirei can't leave Meraiyu?"

He nods. "After Meraiyu down, Saikirei can't leave."

"Water stop Saikirei?"

He shakes his head.

"Other thing."

"Saikirei explain other thing? Difficult explain?"

"Difficult explain," he agrees. "Saikirei try."

Okay, now how does he...

"...Saikirei before, want not die. Saikirei take... thing. Thing do this," he gestures to his cloak, "do this," his glowing green eyes, "do Meraiyu down, do Saikirei not die, do Saikirei not leave Meraiyu. Saikirei only want not die, not want other things."

She nods. Mentally adjusts downward her estimation of how likely it is that Saikirei is just an aberrantly nice omincidal maniac.

She could probably make it to land. She probably has enough air left in her tank that, provided she had a direction to swim in, she could make it to one of the other continents and live out her days there, on the surface, with other people. It'd be dangerous - she's much more likely to die at some point, without Saikirei's help. And the people on the other continents might not speak the same language, so she'd have to go through all of this again, but she could probably do it.

Only she'd have to leave Saikirei behind, and that's not really the sort of thing she can just do. He could've left her to die, and he hasn't, so she's gonna try to repay that in kind.

Somehow.

"How far can Saikirei go? Before thing stop Saikirei?"

"Can touch water. Can touch," he pauses in a vocabulary-related way, "door."

"Door?"

"Before Meraiyu down, Meraiyu have—door. Door to Udimal, door to Lohei, door to Alaila. After down, doors... not. After years, one door go Lohei, little time, then stop. More years, other door go Udimal, little time, then stop. Many more years, other door go Alaila, little time, stop." He makes an and-so-on-and-so-on gesture with one hand. "Doors not, nothing go through doors. Doors go, things go through doors, Saikirei can't go through."

"Hmm. Saikirei can't give thing back." Obviously isn't the sort of thing you can do that with, or he would have done that already. "Saikirei get thing - place?" 

He shrugs and shakes his head. "Difficult explain."

She nods. "Imrainai not go Udimal Lohei Alaila without Saikirei." 

No promises on Earth, but Earth has Ves, and she can't willingly abandon Ves any more than she can abandon Saikirei. Not that going back is likely to be good for her lifespan, even if she does figure out how.

...he smiles. He looks—touched.

Good! Now she just needs to figure out what's keeping him here and how to fix it. Which he's failed to do in more than a hundred of her lifetimes. 

It's good to have goals, anyway.

"Imrainai see doors? Saikirei show Imrainai?"

He nods agreement, and gets up to lead her through the city.

It's a fairly long walk—half an hour or so, in the opposite direction from her crab-hunting grounds at the edge of the bubble. The ceiling gets higher as they walk.

She's gotten more used to long walks over the course of the past few weeks, even though they're otherwise completely outside her experience. She tries making conversation and asking if he knows what particular buildings used to be, a long time ago.

He does know those things! He sometimes struggles to express this knowledge in their mutual vocabulary, but he does his best. This one was a place where people lived, and that one was a place where people wrote things down, and that one was a place where people bought and sold things, and...

...that one was, "Door."

It doesn't look much like a door. It looks like an enormous intricate metal ring made of many partial circles overlapped and layered in complicated ways to form a single circle tall enough that Saikirei could walk through it with two other Saikireis stacked on top of him. The lowest part of the circle is buried under the street, and the rest arches over it.

There isn't anything especially magical-looking about it at the moment. It's just a big round complicated arch thing.

It vaguely reminds her of the gate, although the design is different enough that she wouldn't hold out hope for a common origin even if she weren't on a completely different planet entirely outside the Confederacy.

She walks up and sticks an arm through it, just to check for herself that it doesn't do anything.

It does nothing, exactly as expected.

"Door go place, see place through door," Saikirei explains clumsily. "Not see place, door not go."