VN Ren'Py The Alpha Underground

The Alpha Underground is a sci-fi erotic visual novel set inside a shady underground facility that experiments on its test subjects with muscle-growth research. Francis, a grumpy old bear drowning in debt, gets referred to the place and signs his rights away to become a guinea pig for a perverted but genius scientist. The deal: he gets paid per pound of muscle he gains, so the bigger he gets, the more cash he walks out with.

Built on 2DCG art as a gay furry sci-fi visual novel, the game leans into a male-protagonist focus with male-domination dynamics and dubcon content layered into the experiments. Yama keeps Francis surrounded by other test subjects, masked jacked servants, and every weight he can lift, with the central question being how he holds up under it all.