At first, Sam didn't feel any change in the book, but after checking the book by his system, he can finally see that the technique really got upgraded to B-grade. To upgrade this technique, he uses 12000 upgrade points, but he didn't have any regret.
In previous chapters the fact was established that he has problems to learn techniques of a higher grade than his own. Additionally there were hints that this problem will increase for "super" techniques. But his C-rank Sister will not have any problems learning a very high grade B-rank technique?
At first, Sam didn't feel any change in the book, but after checking the book by his system, he can finally see that the technique really got upgraded to B-grade. To upgrade this technique, he uses 12000 upgrade points, but he didn't have any regret.
Small upgrade system
Fantasy · Small_Otaku