Yuureizaka Higeki(1973)

One winter, a young man named Kouichirou Suda visited the inn run by Hiroko’s family.
Hiroko developed a faint crush on Kouichirou upon seeing him again for the first time in two years, but there was a certain dark shadow about him.
Surgical instruments of unknown purpose, a strict vegetarian diet, a memorial tablet hidden in the closet, and a host of eccentric behaviors…
In fact, Kouichirou had become deeply immersed in the Jina religion, which teaches love for all animals.
Furthermore, having been easily influenced by others since childhood, Kouichirou’s face would come to resemble that of whatever animal he was near.
And Hiroko comes to learn that Kouichirou’s ultimate goal is to bring dead animals back to life through surgeries performed out of love for them…

(Source: Kaiki Manga no Anagura, translated)