You want a power to defeat Demon Lord. You heard from someone that somewhere around this town is hidden the sword the first hero fight with. You found it and then... it starts to talk!

If you desire power then... Marry me! What? You can't marry a demonic sword? Can't be helped. How about this?.

changes into a girl

No problem anymore, right? If you cheat on me with other blades, I won't forgive you, okay? Be it a dragger or cooking knife. You have to always love me and only me, okay~?