There's nothing but trust between them. When Runyu says he won't sink, Ouyang doesn't doubt the truth of it. Though, he does nestle in close against him (just because he can and it seemed like the thing to do in the moment). He enjoys the closeness as they step out onto the water.

Even though he knew Runyu told the truth, he still gasps softly when the water holds his weight. He smiles broadly in the darkness, looking up to Runyu with nothing but awe on his face. The stars were even more beautiful in the center of the pond, where it seems like they are floating in the night sky itself; stars above and below.