The Agony of Authenticity by Lyn Weaver

For as long as he can remember, Kai has hated Sakuya. Sakuya is better than him in every subject, every sport, and every hobby they've both tried, and people actually like Sakuya, even though his charming smiles are fake as hell.

So when they both sign up for a multi-day mountain hike, Kai seizes the chance to expose Sakuya's true colours.

But when the hike goes wrong and the two of them are stranded in a liminal space, one too injured to move and the other slowly succumbing to the corruption in the air, their obsession with each other is the only thing they have left.

Their tattered humanity won't survive the agony of authenticity.