Fantasia: The Realm of Thanos

"Please save Fantasia!" a woman asked you.
She's in front of you, a lonely girl who does not have anyone, asking you to save an unknown world from doom by obtaining a heart key from one of four "strong boys". You decide to do the task, but......

The first one is a Demon Lord....

The second is a bloodthirsty assassin...

The third is a mysterious hooded guy...