Unkoman

One day, a boy with amnesia wakes up and finds himself falling from the sky. Due to his amnesia, he does not know his own name. Depending on the route he is given various different names such as "Ozaki Kiyohiko" (based on Japanese singer and actor Ozaki Kiyohiko), "Yuuma", or "Hideo". Shitman (うんこマン) is the nickname given to him by Goddess. (Source: VNDB)