I Can't Exploit it Because of the Expectations and Evaluation from Slaves

Allen is reborn in a new world, and a goddess gives him a cheat skill called Regeneration. It can heal any injury or disease, but there isn't much call for that, so he comes up with a plan: heal a group of slave girls and settle into a slow life with a harem. It doesn't go the way he pictured. Once the girls are fully healed, their own abilities turn out to be far beyond his. The crops grow almost overnight, and the living conditions improve just as fast. Allen keeps getting edged out of any useful role. He falls back on the modern knowledge from his past life, but the girls pick that up too and turn it into a hugely successful business. Allen is slowly fading into the background of his own story...?!