Sasagawa Takashi, a 17 year old boy that works at the local Guild to earn some money for his sick Mother because his Father has already died 3 years ago, Takashi's Mother is infected with the rare disease named "Deep Sleep", a disease that puts the infected person in a never ending slumber. Takashi not only have to take care of his sick Mother, but also his little Sister.
Today, Takashi has to go to the dungeons to slay magical beasts to get magical gems. Selling magical gems and corpses of beasts is Takashi's main source of income, but he has to join a guild to enter said dungeons.
*later inside the dungeon*
Takashi is fighting magical beasts and collecting the magical gems that said beasts drop after dying, as Takashi was heading outside he accidentally stepped on a trap which exploded in his feet putting him on a life or death situation, but then.....
A being that looked like a "Devil" on the left side and an "Angel" on the right suddenly came out of the hole made from the explosion.
Along with this being, magical beasts from lower floors of the dungeon also appeared, whom Takashi couldn't beat even if he was at best condition.
[You are currently on the brink of death, i shall give you a choice as a showing of my gratitude for freeing me from that "Seal"]
Said the mysterious being
For some reason this being could read Takashi's mind and said
[I shall give you 2 choices.
1) I shall heal your Mother and revive your Father, but you will be sent to a place known as "The Lost Castle".
2) I shall heal you from your current condition.]
Takashi thought about it for a second, but hesitantly took the 1st choice as he knows himself he can't beat those magical beasts from lower floors of the dungeon, thus Takashi was sent to the "Lost Castle" and what he saw surprised him....