Ore ni Dake Mieru Make Heroine (Fukusuu) ga Geki-Omoi Kanjou Sugiru (sainokantls.com)

Protagonists and harems go hand in hand. However, only one gets chosen. This is an unchanging fact throughout all times and places. The heroine who wasn't chosen by the protagonist and went unrewarded──in other words, the lamentable losing heroine. The future of a losing heroine is miserable. She can't be with the guy…