My 13 year old got some Birthday Money from friends and relatives and wants to buy a 1 metre long Japanese Kantata sword with the cash to display in his bedroom... They say they would put it away when friends visit and that they can legally buy it but I'm not very comfortable with the idea. DS is generally sensible and very interested in sword fighting. Generally I'm ok with him spending his own money as he wants but would it be irresponsible not to block this? Thanks!