It's a manga that's been running for 20+ years now, and it's pretty incredible. One of the things that's most interesting about it, is that the author has basically reinvented himself in his style several times throughout the series, while still keeping it true to its roots. During the first 10 volumes (referred to collectively as the "Golden Age" arc), it's basically gritty 80s style manga of purely dark medieval warfare, becoming borderlined historical fiction. but in volumes 11-12+ literally hell opens up and pours itself onto earth evil dead style but in a completely serious manner. Over the next ~5 volumes you have every bit of bad in his world corrupted and risen to full blown demonic rape-fests; corrupt priests burning everyone at the stake, packs of roving goblins kidnapping women, raping and impregnating them to make more monsters, an evil god-emporer who tries to take over the world etc. It then turns into a traditional swords/sorcery fantasy where Guts assembles a team of rag-tag heroes to destroy the five God Hands of hell, one of whom was his best friend and rival during the Golden Age.
Yep, and by then Guts rejects Griffith, which Griffith can't accept, and kind of fucks everything up because of it
Nicholas Cox
You need a fucking life dude
Grayson Parker
Guts must've been so disappointed. He finally had learned to love someone (Casca) and had people he could call friends/comerades (BotH), then he thought he had a special relationship with Griffith, but it turns out Griffith just seemed to be using him. I can't blame Guts for leaving, it's Griffith's fault for treating Guts as a pawn, when Guts deserved better.