Wow, another plot twist! Founder was alive after all WTF?!

To be frank, the concept of kekkai-jutsu is refreshing but somehow I got the impression that the mangaka is having a hard time organizing the plot & flow... they felt kind of jumpy, if you get what I mean. One moment this, then that & suddenly a strong ally that has been around all these while decided to appear but where was he when Karasumori was under attack by the enemies?