How/when does Kinu grow up? Does she need to leave the orb first?

[Raindrops]

As title

I have done much porking of Kiyoko over my playthroughs, but I've never actually seen Kinu grow up

I have also never freed her (I only found the option to do so a week ago or so, and I'm currently aiming for 32 kits minimum before going through with that), and I'm wondering if that's related?

 

[Lotus]

She is an adult when she leaves the orb.

 

[WolframL]

Yeah, it's something that's sprung on the player when Keros frees Kiyoko, Kinu and any other children you have from the Astral Plane, as part of his whole equivalent exchange schtick.