Complex sentence: Yoshimitsu's great-grandson, Nobuyoshi, eventually took the surname "Takeda", and the techniques Yoshimitsu discovered would be secretly passed down within the Takeda clan until the late 19th century, when Takeda Sokaku began teaching them to the public.
Split into simpler sentences: Yoshimitsu's great-grandson, Nobuyoshi, eventually took the surname "Takeda". The techniques Yoshimitsu discovered would then be secretly passed down within the Takeda clan in Japan until the late 19th century, when Takeda Sokaku began teaching them to the public.