Itomimizu

The main character Satake, who was being bullied in a rural village, accidentally kills Katsuya, his classmate and bully. Hell begins when Katsuya's girlfriend, Yumeno Kujou, somehow finds out about this... Rumors, jealousy, and bullying unfold in this isolated village. All of these things push Satake into a corner... Conceal the murder and survive!

(Source: Kodansha, translated)