not sure if to difficult for me after demo

Hello. So, I played through the demo in 13 hours. I got stuck on the last boss, Jakotsu Baba, for a very long time. After about 20 attempts, I summoned a helper. He somehow held the aggro and I just had to hit him in the back and managed to do it that way. But that didn't count as a victory for me. I only put 2 talent points into Heart afterwards and tried again on my own. Then I only needed 3 attempts. I hadn't changed anything else. I'm unsure because it was suddenly so much easier, whether there was some kind of buff and the rest might be too difficult. Do you know if there was anything after defeating him?

Translated with DeepL.com (free version)