am surprised the mc didn't jus take the money and go back to training

Lol I thought the same until he started his plan, then I just repeatedly whispered to myself "oh no..." As he constructed the slave training

those kids gonna be scarred for life bc of his training, he learned from his master after all loll it'll be fun to see them cry as he did

Imagine when his master finds out about it. Instead of if being simply slave training it will become "eternal" slave training. Especially when his master sniffs the money

But I’m selfish ╥﹏╥ i don’t want them to know all his technics and training ╥﹏╥ ╥﹏╥

i doubt that'll happen. all of his training sessions take months to years so at most he'll be advancing their strength, accuracy, and agility. he'll probably be showing them only the basics which require a lot of diligence/determination to finish so if they can master what he shows them i feel like they've earned it. that's my take on it.