Rewrite - The Simple-Looking Sword Saint is Nevertheless the Strongest

[Following the story until chapter 15 in the Manga] Listening to Eckesachs story about his masters past Sansui our Protagonist wakes up from the Spirit Will which imprisoned his mind for over 500 years. What will he do now since he realized that he was betrayed and lied to? Note: I hate how good the manga started and how stupid it proceeded. I am trying to rewrite it to my liking but still use common sense while doing that. I am from Germany so excuse my mistakes while writing.