Berserk: Ougon Jidai-hen I - Haou no Tamago

Guts, a mercenary in the Kingdom of Midland prefers a conflict-filled life to a peaceful one. He is unstoppable, even though the odds are never in his favor. His massive sword, which is larger than he himself, allows him to overcome any opponent.
Griffith, the mysterious head of the Band of the Hawk mercenary squad, sees the swordsman's fighting prowess one day and invites him to his squadron. Guts, who initially refused the invitation, challenges Griffith to duel, and, to Griffith's shock, is defeated. Guts then joins the squadron.

Guts will now fight with Griffith to defeat the Empire of Chuder. Griffith, however, seems to have ulterior motives and wants something bigger than just ending the war.