I will be honest, this fangame is the biggest ragebait in history. The homing star attacks are genuinely nigh impossible to dodge, the sword tunnel attack is impossible to react to unless you already know whats coming, the gimmick of the fight is not explained. Once you figure out what you are meant to do you will still not be able to win the fight due to how perfectly the fight has to be played, you genuinely have to become a god of dodging and grazing to get enough tp to win the fight before kris collapses from the passive damage; the fight is on a very strict timer. this fangame took me an hour and 40 mins to beat, 4/10. There should be a way to lower kris's passive damage.
Viewing post in DELTARUNE - Alternate Ending - Chapter 7A Kris VS Susie comments
you can give healing items for Kris/use overheal on Kris to extend the 'timer' significantly
usually I'd defend turn 1 and 2, overheal turn 3, take the shadowmantle turn 4, and use festivemoss turn 5 to get both of their HP back up
probably use a bunkerration after the first [lower guard] and the spincake after the second, to keep Kris's HP up
this is not the first time people have had issues with the star attacks, I don't really get why people find them so difficult, but I might add an option to make those easier at some point if this many people struggle with them so much