I thought that was a really good ending with Teppei & Daisuke being a callback to Kenji & Masaomi. The fact that both Kenji & Teppei were being provocative in front of Masaomi & Daisuke made me wonder if that behavior was encouraged as part of the treatment.
What got totally ignored was Gender Dysphoria, it didn't appear that those chosen were volunteers and I would've thought that living as the wrong sex/gender could end in suicide in certain cases.