Step one: Get Neiro's permission."Mind if I have a lick?"
She's just like me! I wanna lick Neiro-sama too!
But on the other hand, it's like starting a relationship the author can't write. Do it in the last chapter, since then it doesn't actually affect anything. Not that readers tend to be very happy about that, but it's how it often goes. And a "return to normal for a normal life," is a very common ending theme.I doubt the author will back away from the giant girl gimmick this late in the game,
i prefer 2,So two things, either
1. Either Chieri goes back to normal, fulfilling her biggest wish being lovers with Yuiji
2.Yuiji turns into a giant as well, giving them everlasting connection together on the same level.
1 might be likely, but 2 feels the most satisfying to me and would be a unique take