This is GTN, it's a coin flip as to who will show up on the paternity test... if either of them are shown to be the father.
this would be conception by a lesbian couple using a sperm donor i guess, though whether the donor himself was willing... would be another question if we want to guess who has legal custody.
the insemination by spitting cum at hydraulic waterjets though is very gtn, and strangely in character (i guess????) if noa ever wanted to get yuuka knocked up