Alfheim no Kishi

From Friendship Scans:

Princess Rosely’s fate was sealed when she first picked up a sword to try to kill an evil wizard. Little did she know the legendary Lucilys, Sword of Light, had chosen her to be its heiress, bringing her peaceful life in the castle of Altodias to ruin.

Soon, the young princess encounters the pain of losing all the people that she loved, and being separated from her twin brother Rolant, the heir of Silvan, the Sword of the Moon. Rosely would have been even dead floating in a cold river if she had not been saved by a handsome green-eyed king of the Alf.

Growing up as the king's foster daughter in Alfheim, Rosely learns magic and martial arts from the Alf, only waiting for the day she can avenge for her lost country. Will she be able to fulfill her will? What does the fatal sword Lucilys have in store for her? Will resentment drive her into insanity? Who was the one behind all her misfortunes? And who could have been the chosen owner of Soles—Sword of Sunshine, the third one in three ancient magic swords?

This fantastic tale will make you want to believe in fairies again!