Guts (sometimes Gatts or Gattsu) is the anti hero protagonist of the Manga series Berserk which originated in 1988, with a 42 page special. Since then has grown to over 290 chapters.
In the beginning we find him being betrayed by his best friend and he is being chased by demons, and this is where the story begins; Guts must force his way through hordes upon hordes of demons looking for his revenge upon Griffith, the man who betrayed him.
It is the mark on the back of Guts' neck that summons the demons to him, and because of this is cursed never to have another night of rest.
In his first game appearance Sword of the Berserk: Guts' Rage (which takes place between volume 22 and 23 of the manga) he is travelling with companions Casca and Puck. He is searching for a cure for Casca's traumatization and end up saving a village.
In this game Guts uses a huge sword (roughly 8 foot in length and a foot wide) and must slash his way through enemies. Guts is usually outfitted all in black, and retains his apprerance straight from the manga.
In his second game Berserk Millennium Falcon Hen Seima Senki no Shō Guts follows the main story for the volumes from 22 up to 27, however like the manga we see the same Guts as in the previous game.