Anime about girls called fairies that fight demons on Earth. The main character is a guy that fought one of the demons with 3 friends, 2 of the friends died in the fight and he killed the demon but got frozen in time.
When he gets unfrozen he gets a job to look after the girls. During the job he learns the girls are called fairies and use swords that no one else can use to kill the demons. The fairies don’t live past the age of 15 and die to the demons or to the memories of there past lives. So he teaches them how to fight and also repairs their swords in the hopes they would live longer.
He falls in love with one of the girls/fairies; she has blue hair and is the strongest fighter and she dies in the end and gets reborn again. That’s all I can remember, doesn’t anyone know what this is?