Yui and Zen

This is a story placed in the past where technology don't exist. In a world where mana and demon exists. There are 4 elements of mana: fire, earth, water and air. Then there's the exception, cursed mana, a very rare but powerful mana. But this story starts with a boy. A boy who dreamt of being the strongest samurai, the same with his twin brother. But it was clear, they were both on different paths. Both of them were borned with cursed mana.. Zen our main character lost his twin brother in a horrendous accident where a mysterious masked demon wiped out the entire village. Zen was lucky as he was in mountains training. His twin brother, Yui suddenly disappeared. No body no scent and when Zen looking around his village enlightened by purple flames, he vowed to find his brother. His twin, the last member of his family.