i need some help

A friend comes over to play some lol, we used his account, now he left, I put my name in the username field and connect everything works fine,but the thing I hate is I have his runes, and every time I restart the client his name is there (of his account) I need to change it to mine, and then the runes are the same as his, I need to change them everytime if I rename "Shadow Assasin" into "Yasuo" and change runes, when I restart I have "Shadow Assasin"

I don't know what to do, I'm sorry for bad English I don't know how to explain very well I don't know if you understand, if you don't I will try to explain better