Watashi wo Yashinatte! Yuusha-sama

After our protagonist helps out a girl dressed as an elf at a doujinshi event, she starts following him around, calling him "Hero-sama." He thought she was just role-laying, but it seems like the girl is actually serious about it… The story about the difficulties of daily life between an amnesiac elf and an ordinary guy! (Source: Kadokawa, translated)