let'sgoooooooo
sorry for confusing... in knife deleting part you need to drag & drop 10 knife skills that you already own(the things on the right is the placeholder for delete). When you filled all of the blank on the right side , you can now press the rebirth button. (I checked the part of the system is not made well and causing a trouble so fix I'm working on it to fix & I think I need to improve the UI on the part so will do it together)