If you pull 400 seals in GNW its all about luck since some people pulled 400+ and got dupes before even getting the ninjas they want. Even friends of mine did the 300 pulls you need to get all the rewards from the rebate event and they didn't get the 1 ninja they need but dupes instead so its really your choice if you need a team right now or if you can wait and save more seals again and pulls again after your 400 seals in GNW. And depending on your power kushimaru might be overhyped since most of his damage is from just being high power vs lower power