: Tsukasa tracks them down and takes Yuzuriha hostage. He offers to spare Senku's life if he renounces science forever. Senku refuses, choosing to die for his beliefs rather than live without science.
You can watch (including episode 4) with Italian subtitles on major streaming platforms: Dr. Stone Episode 4 Anime Review - DoubleSama Stai guardando DrStone Ep 04 SUB ITA
In this pivotal episode, the conflict between Senku's scientific vision and Tsukasa's idealized "Stone World" reaches a breaking point: : Tsukasa tracks them down and takes Yuzuriha hostage
: The episode ends with Tsukasa delivering what appears to be a fatal blow to Senku's neck. Where to Watch with Subtitles Stai guardando DrStone Ep 04 SUB ITA
: Senku, Taiju, and Yuzuriha travel to Mt. Hakone to collect sulfur, the final ingredient needed to create gunpowder.