Maryoku 0 de Tsuihou saremashita ga, Daiseirei to Keiyaku shi Maken no Chikara ga Kakusei shimashita

Elias, an orphan, is given a demonic sword by the master who looked after him. He then joins the hero party in their adventures, However, he's unable to draw out the sword's power, and is eventually expelled from the party as useless. Starting out on his own as an adventurer, he encounters Emma, an elf girl being chased by a dragon. He and Emma join forces to fight the dragon and, with unexpected aid from a helpful spirit named Undine, manage to defeat the dragon. Elias, Emma, and Undine then set off for the elf kingdom together.